Off-road Bush Mechanics and Maintenance

4x4-africa - off-road bush mechanicsOff-Road Bush Mechanics

Of all the things Bud, our aspiring off-road driver feared most, having his 4×4 break down in the bush was top of the list. Bush mechanics or any other sort of mechanics was not his strong suit, and the more he thought about the mechanical and electronic complexities of his 4WD, the more he became convinced that if the worst came to the worst and he had a serious breakdown, especially while he was in the depths of Africa, he would be in deep trouble.
4x4-africa-road-side-repairsThings did not look so bleak in South Africa, or even the larger Southern African region, where his insurance company assured him that even if it were the last thing they ever did, they would find him and get him mobile again via their roadside assistance scheme, even if it took them several days to do so. However, this arrangement seemed somewhat less than ideal, so Bud obtained repair manuals for both his 4WD vehicles in an effort to penetrate the arcane black arts of modern 4×4 design, construction, and repair procedures. Sadly, though, although Bud was now able to at least identify some of the major components on both his 4×4’s, the systematic instructions seemed only slightly less complicated than celestial mechanics even though they were accompanied by photographs, so, Bud called the Instructor at the off-road club to book his place in the upcoming lecture day, during which there would be a lecture on both bush mechanics and preventative 4×4 maintenance.
The Instructor had assured Bud that bush mechanics sounded worse than it actually was, but just to be sure, Bud decided to record the lecture, the edited transcript of which is reproduced here:

Bush Mechanic Contents:

Preventative maintenance

“OK, so some of you are concerned about what happens if you break down in the bush, especially in the hinterland of Africa, where there are not many repair facilities, and even fewer mechanics. Breakdowns do occur of course, but the truth is that modern 4WD’s are extremely tough and reliable. The trick in avoiding or preventing break downs lies in maintaining your 4WD in such a way that breakdowns are unlikely, because the last thing you want, or have to do, is to prove how good you are at bush mechanics.”
“Common sense dictates that a poorly maintained 4×4 is more likely to break down than a well maintained one, and if I had ten bucks for every time I came across a 4×4 that broke down because of poor general maintenance, I would be rich today. However, breakdowns cannot be eliminated altogether, but there are certain things you can do to lessen the likelihood of it happening to a large degree, and if you stick to the following points, you should be OK, breakdown-wise.”

Service regularly!

“Remember that maintenance schedules apply to vehicles that are used in the urban environment since manufacturers cannot establish service schedules for every 4WD vehicle used in all conditions. Also, remember that the demands of off-road driving are such that some components and systems need more frequent inspection and servicing than the manufacturers recommend. For instance, because of the fact that most 4×4 vehicles are almost exclusively used in dusty conditions, the brakes will wear out long before the recommended replacement interval. Similarly, items like ball joints, tie rod ends, and universal joints on drive shafts are not water- and dust proof, which means that they need more frequent inspection and replacement than a 4WD that spends most of its life on tarred roads.”

“By the same token, just one deep water crossing can ruin your differentials, wheel bearings, drive shafts, and transmission because of water contamination of the lubricants. The damage might not be immediately apparent, but say you neglected to check for water contamination of the lubricants and you start to hear a whining sound from both differentials on your next trip through Africa. Now you are in trouble: the damage is done, and will only get worse; you have no chance of repairing your differentials in the bush, and even less chance of finding replacements.”

“If you are new to off-road driving, always remember that even authorized agents only do what you ask them to do when you take your 4×4 for servicing or repairs: it is rare to find a workshop that will go out of its way to find and report all the faults on a vehicle. Therefore, if you do not do your own maintenance, the thing to do is to find a workshop that performs safety checks on vehicles, and the more points they have on their list, the better. These workshops use safety checks as a business model to generate extra work on a vehicle when it is presented for servicing, so have your 4×4 serviced and checked every time you return from a long off-road excursion. It may be expensive, but remember that this workshop depends on the extra work to survive, and that your life may depend on them finding and correcting potentially dangerous defects on your 4WD.”

“One final thing to keep in mind if you do not want to break down in the bush is the fact that every service you do on your 4WD should be a major service. A major service must include the following, apart from the obvious replacement of all filters, spark plugs, lubricants, draining of water traps in the fuel system, and a diagnostic check of the electrical system.”

Pressure test the cooling system

“Even if there are no visible coolant leaks, a pressure test will reveal any issues with internal leaks that may have developed since the last service. Coolant seepage past a head gasket might be so slow that it may not be apparent, especially if you are not a mechanic, so have the cooling system pressure tested, and the engine oil checked for the presence of coolant and exhaust gasses, just make doubly sure the cooling system in perfect condition.”

Test the engine compression

“A regularly serviced engine, and especially one that runs on synthetic oil, should not have compression issues, however, due to the nature of off-road driving, small amounts of dust may have been entering the engine through leaks in the intake system that you may have been unaware of. However, a loss of compression is not always caused by dust ingress, nor is it always accompanied by visible exhaust smoke or an increase in oil consumption. Defective fuel injectors can sometimes wash the lubrication oil film off the cylinder walls, which has the effect of dramatically increasing mechanical wear between the cylinder walls and the piston rings.”

“Even engines in perfect condition may show slight differences in compression between individual cylinders, but this never more than about 3 or 4 percent and usually not enough even to cause a slight misfire or uneven idling. Differences in compression that is bigger than 5-7% could be evidence of an incipient problem, especially on diesel engines since a diesel engine depends on compression for ignition and proper combustion.

Check the brake system

“The mere fact that your 4×4 stops when you press the brake pedal does necessarily not mean that the brake system is in good condition. Brake discs and drums may be excessively worn, or worse, cracked, and the only way to check for this is to remove the wheels so that you can see exactly what is going on. Oil leaks on side shaft seals may also only become visible with the brake drums removed, so mark the wheel nuts, or bolts with a small inconspicuous spot of paint or nail varnish in such a way that the mark is broken when the nut or bolt is removed. This will go some way to proving that a proper inspection of the brakes had been performed.”

“Also, insist that the working pressure of the brake system is measured; a properly equipped workshop will have pressure gauges made for the purpose. With long time use, you may have become used to the brakes not working as well as they used to, so, make a point of having the brakes pressure tested on a regular basis.”

“Which reminds me; one thing that is very often overlooked is the high pressure flexible brake hoses on the front wheels. In urban driving, these hoses last for as long as the 4×4; however, in the off-road environment these hoses flex a few million times more often than they will on a street vehicle. What happens is that the inner layers of the hose separate from the braided reinforcing layer around the point where the steel fitting is crimped onto the rubber hose. The separated layers then act like non-return valves, allowing the brake fluid to pass into the caliper, but preventing the brake fluid to return, which is how the brakes are released. When this happens, the brakes on the affected wheel can bind, causing the brakes to overheat and destroy not only the disc and the pads, but also very often the wheel bearings as well because of the excessive heat build-up that melts out the grease. In a severe case, the brakes can lock unexpectedly and the only way to fix that is to replace the hose.”

“Therefore, to avoid this, have the flexible hoses replaced at least every two years, which probably equates to around ten years of urban driving. Make sure you get them only from the authorized agent for your 4×4 though, because if you have them fabricated somewhere, you can never be sure they will not fail the second time you apply the brakes.”

Check for relative movement in the steering and suspension

“Ball joints, tie rod ends, and universal joints are not service items, and many, if not most mechanics will not check them for wear unless you tell them to. Slight relative movements between the component parts of these items may not be noticeable at first, but any relative movement will increase exponentially with continued use. A sudden impact on a rock, or a rut can cause a worn ball joint to separate from its cage, which when this happens, means that a principal mounting point of a wheel to the suspension has become undone. This is a serious issue: you will instantly lose directional control, the brakes, and very possibly the entire 4WD vehicle as well as your life when you fall down the side of a mountain.”

“Have your suspension and steering checked every time you have been off-road: damage or wear that may not at first be visible or apparent could cause you break down in the middle of the Nubian Desert in Egypt, which is no place to demonstrate your skill at bush mechanics.”

“Similarly, have the universal joints, CV joints, centre bearings or other couplings in your prop shaft checked every time you have been off-road: universal- and CV joints should have no free play in them, but if they do, replace them with genuine OEM parts immediately. If you do not, the wear will increase exponentially until the universal joint disintegrates, which could be before the vibration caused by the unbalanced prop shaft damages your transmission. A disintegrating universal joint can break the yokes holding the shaft together, and if this happens, the part of the prop shaft still attached to the engine will start flailing around under the 4WD, destroying everything it meets. This type of damage cannot be repaired in the bush, no matter how good you are at bush mechanics: rather spend the relatively small amount to ensure your prop shaft is reliable, than spend the fortune required to recover your 4×4 from the depths of Africa.”

Check the electrical system

“More break downs are caused by electrical and cooling system issues than all other causes combined, so have the electrical system on your 4×4 diagnosed at least three times every year. If you have a diagnostic function, so much the better, but if you do not, have the wiring harness inspected for rusted and corroded connectors. The wiring diagrams in repair manuals always list the voltages and resistances at all connections as well, so rather spend the money to have the system checked properly, than spend a fortune in replacing a vehicle that caught fire because of short circuits and bad connections.”

“Make a particular point of having the charge rate of the alternator checked, which should always be between 14.2 and 14.6 Volts, as well as the form of the electro-magnetic wave it generates. This wave has a specific form and deviations from this form indicate problems with either the windings or the diodes in the rectifier. Consider the fact that without electrical power, your 4×4 is dead, and so might you be if your battery power runs out a thousand kms or more from anywhere. The fact that the alternator warning light does not illuminate is not necessarily an indicator of the health of your alternator, so, spend the relatively small amount to have it tested by a competent auto electrician- your life might depend on it.”

“If you have electrical accessories, or plan on installing any, make sure you have wiring diagrams of those accessories. Such a diagram should list the components, the colours and thicknesses of the wiring used, as well as the location and capacities of fuses and relays used in the installation. In addition, regardless of whether you install electrical accessories yourself, or having it done, all connections should be soldered and the wiring included in the main harness covering. Wires that run willy-nilly all over the place can chafe through and cause potentially catastrophic short circuits, and the middle of the equatorial rain forests of Africa during the monsoon season is no place to try and replace a wiring harness, supposing you have a spare, which you almost certainly do not, but there is an equally important aspect of your electrical system, and that is your battery.”

Check the battery

“It is a sad fact, but the quality of automotive batteries sold in South Africa is among the worst in the world, which when coupled to the fact that there is not much you can do to fix a failed battery in the bush means that you have to take very good care of your battery, because they are not designed to last more than 18 months or so.”

“The problem with batteries is the fact that they develop a “charge, or cyclic memory”, or crystalline formation, which means that over time, a battery “learns” to “remember”, in a chemical sense the maximum and minimum rates and levels of charge it is subjected to, however, new generation batteries, such as the nickel-cadmium variety have largely eliminated the cyclic memory phenomenon. In practice though, old lead-acid style batteries are still plentiful and this means that if a lead acid battery is drained below its “learned” minimum charge, like for instance during a demanding recovery with a winch, that battery may refuse to take another charge. Such a battery is essentially dead and cannot be revived, which means that even the most skilled bush mechanics cannot save it.”

“However, there is a type of battery, called a deep cycle battery; which do not develop charge memories and can be repeatedly drained completely and then recharged, all with no ill effects whatsoever, but even these batteries are not infallible. For instance, they can be damaged and destroyed by an alternator that over-or under charges even just a little bit. They can also be damaged by short circuits, such as during jump-starts when polarities could be accidentally reversed or by general faults and short circuits in the wiring harness due to moisture or mechanical damage.”

“In addition, bear in mind that a damaged battery, such as one that has a difference in the specific gravity of the electrolyte between cells, can damage an alternator, or other critical components such as the engine and fuel management systems because of the reduced voltages. If this happens, you are stuck; no amount of bush mechanics will get that 4×4 mobile again short of replacing all the electronics, because this type of failure often has a domino effect; if one thing fails, several others do as well- almost as if in sympathy with the original failure.”

“Nevertheless, the old adage that prevention is better than cure, applies to batteries more than to anything else when it relates to bush mechanics. If you can get the parts, it is possible to rebuild a 4×4 engine in the bush, but you cannot fix a damaged battery, and as far as finding replacement parts in Africa goes, batteries are more difficult to find than anything else is, especially north of a line drawn between the northern borders of Angola and Mozambique.”

“However, all is not gloom and doom; there are several things you can do to prevent any of this happening to you, such as:

Use the right battery

“One of the most common causes of battery and general electrical failures is due to the fact that the battery is not capable of delivering the amperages needed to start engines, and diesel engines in particular. An under rated battery might work perfectly for a while, but it will be damaged right from the first engine start, even if the damage is not immediately apparent. Diesel engines require a whole lot more power to turn over than a petrol engine because of their higher compression ratios, and if the intention was to save a few hundred bucks by fitting a lower rated battery, you will pay for it later in ruined starter motors, exploded glow plugs, and destroyed electronics. If you have an electric winch, the smaller battery will almost certainly damage its motor because it cannot draw the amps it needs to work to its rated capacity, just like the starter motor.”

“Bush mechanics cannot repair the damage caused by under rated batteries; if the manufacturer of your 4×4 tells you to use a specific battery with a prescribed amperage rating, do not use anything else. It is a bit like the medicine prescribed by your doctor; using too little does not cure the disease, and it could actively harm you. Similarly, taking too large a dose, as if using an over rated battery, does not work twice as well; while it might fight the disease, it could harm you in ways that cannot always be predicted, or repaired. So, use the correct battery for your 4WD, and you will not have to demonstrate your bush mechanics skills.”

“One last thing to keep in mind is the fact that sealed batteries are always better for off-road use. Apart from the fact that they are maintenance free, they are sealed against the ingress of water, dust, and other contaminants. As long as you use the highest quality terminals and cables you can find, you should not have any problems with your batteries. Your batteries can be compared to your heart; without it to supply power to your 4×4, your 4×4 is dead, as you will be if your heart fails. While the alternator might be able to supply power on its own for a while, the current draws of modern engine and fuel management systems are such that by itself, no alternator can last very long.”

“Some older diesel 4×4’s can run forever without a battery or an alternator, but these days those are few and far between, but no petrol engine can run without electrical power, so, look after your battery, and it will look after you.”

Fit a battery isolator

“Many professional mechanics, me included, have at various times in our careers spent days and weeks trying to find the source of a permanent drain on battery power on vehicles ranging from old Land Rovers to Lamborghinis. It is a common problem and in many cases, the problem is never found and resolved. In addition, tracking devices draw more current than you might think, but as I said, the problem might never be found, so, if you have this problem on your 4×4, fit an isolating switch that you can turn off when you park for long periods, because in the off-road world, you need your battery to be in peak condition at all times.”

“If you do not have a deep cycle battery, fitting an isolator will save your battery from damage when you try to recharge it after it had run down, but that is only part of it. Attempting to start any vehicle with a partially run down battery could damage the starter motor as well as any number of electronic circuits, again because of the lower than required voltages as well as amperages. A starter motor that is starved of current will try to compensate by drawing all the available current in one go, something that could destroy both the battery and the starter motor. You might then be tempted to jump start your 4×4 if there is another one available, but whatever was not damaged during the starting attempt with the flat battery, might now be damaged because of the voltage spike if you get the connection sequence wrong.”

Jump starts

“Many people, mechanics included, often go about jump starting a vehicle the wrong way, and it sometimes seems miraculous that the electronics survive. Modern electronics are extremely sensitive to voltage drops and spikes, so, it is very important to follow the jump-starting procedures for your particular 4×4 exactly. Jump-starts should of course be avoided as far as possible, but if there is no other way to start your 4WD, make sure the cables are rated at least 400 Amps, to ensure that enough current passes through them.”

“Most modern vehicles have a dedicated connection point for the positive cable: using this point ensures that the starting current follows the correct route, so never use any other connection point if there is a dedicated one. Next, make sure that both vehicles are switched off and not in direct contact with each other before the last connections are made. This is to ensure that no sudden voltage spikes run through their electrical systems, and only once the last connection is made should the starting 4×4 be started and kept at a fast idle for at least 5 minutes before the lights, wipers, and internal fan of the 4×4 with the flat battery are turned on. By turning on the heaviest electrical consumers, the possibility of voltage spikes is largely eliminated. Then, and only then, should you try to start the 4×4 with the flat battery. If it does not start immediately, stop trying, turn off all the electrical consumers, and continue charging the battery with the alternator of the other vehicle.”

“If, after following the same procedure, the vehicle does not start, rather go to the trouble of swopping batteries with another vehicle: once you have started it with a fully charged battery, let it warm up. Once it is good and hot, it might start with its own battery, but if it does not, a jump-start from the second vehicle will almost certainly start it. If it still does not start, there is something else wrong, like for instance, defective glow plugs, or a vacuum leak in the fuel system, and the fault should be found and fixed before both vehicles suffer damage to their batteries and electrical systems.”

“The only way to avoid all of this is to ensure you have a healthy battery, even if you have to replace it every year. Batteries are not as cheap as they used to be, but compare the cost of a battery to the cost of recovering your 4WD form where it broke down in the hinterland of Africa. The recovery cost could be several times what your 4×4 is worth, or as has happened in the past, you might never get it back, because someone stole it.”

Fit a dual battery system

“Fit another battery; one that is isolated from the vehicle’s main electrical system, but in such a way that it provides power to the winch and all the other electrical accessories you might have. This way, you will save your primary battery from the loads a winch demands, and you will have a spare battery if the primary unit should fail for whatever reason. Of course, a second battery takes up space in the engine compartment, so mount it where it is out of harm’s way, such as far away from the turbo charger or exhaust manifold. It must also be high enough not to be immersed during deep-water crossings.”

“Also, keep in mind that you may have to upgrade the alternator to be able to cope with the added load, and if you have to mount the second battery some distance away, such as in the load bed, make sure it cannot come into contact with water, fuel, and food stuffs. In addition, make sure the poles cannot short out, and that there is provision for the highly explosive hydrogen gas that is released during charging to vent safely. That is not all though; also make sure that all the wiring and cabling associated with this battery is rated for the task, and that all the additional wiring and cabling is protected against chafing, rubbing, and other possible damage.”

“This might sound like a lot of hassle, but you will be glad you did it when the time comes that you need a second battery, so once again, look after your battery.”

Wheel bearings

“A single deep water crossing with hot wheel hubs is enough to allow water to enter the wheel bearings through seals and grease caps, so, have the bearings and the grease in them inspected as soon as you can after you have crossed deep water. Some types of grease, such as specialized marine greases are better at repelling water than other types, but once water enters the mix, the bearings will rust, and while it might take some time for the damage to become apparent, the last thing you want to have happen is having a bearing seizure or collapse in the middle of the Kalahari desert. A bearing seizure can literally weld some of the bearing components to the stub axle, and sometimes the only way to remove them is by using an angle grinder to cut them off. However, even if you have spare bearings, the chance that either the stub axle, or the bearing housing in the hub, is damaged beyond repair is almost guaranteed, so, once again, spend the money to have them checked and replaced if there is the slightest doubt about their condition.”

Drive belts and hoses

“Radiator hoses are cheap enough to replace every year. Always having new hoses means you do not have to spend time and energy worrying about how to repair that bottom hose that looks like a balloon because of the oil that had been dripping onto it. That same oil leak your mechanic told you was not worth the expense to fix; and is now threatening to leave you stranded a thousand kms from any form of civilization. You should have spent the money to fix the oil leak: the cost of it was certainly less than what the recovery cost from, say, Ethiopia is sure to be.”

“Much the same thing goes for V- and other drive belts. Drive belts do not just fail; they fail for a reason, and the most common reasons are damaged pulleys, incorrect tensioning, oil contamination, and misalignment, whether through failing tensioner pulley bearings, or misaligned components. This aspect of belt maintenance is particularly important on engines that use serpentine belts, because if the belt fails for whatever reason, you could lose the power steering, the brakes, the water pump, the alternator, or a combination of any of these systems.”

“You can do without power steering, but you cannot do without the water pump and the alternator, or the brakes on vehicles that have belt-driven vacuum pumps, so have your drive belts inspected at least once a month for damage or misalignment, or immediately, if you become aware of squealing, or any other mechanical noises that vary with engine speed.”

Bush mechanics explained

“So far, we haven’t said much about actually repairing a broken down 4WD in the bush, but you should not have to repair anything if you have been maintaining your 4×4 properly. If you do all the things we have just discussed, the chances of you breaking down are extremely small; however, breakdowns do occur, so let us look at some of the things you can do if it happens:

Cooling system

“One of the best ways to prevent cooling system issues is to install an electric water pump, an electric radiator fan, and an electronically controlled thermostat. While the first two are relatively easy, installing an electric radiator fan might not be. There are several reasons for this, the most common being lack of space, but if you can fit one, have it done by a specialist in engine cooling; fitting an electric fan just for the sake of having one might be more trouble than it is worth, since an ineffective fan and shroud could cause sudden and catastrophic overheating; a situation in which no amount of expertise in bush mechanics is going to be of any use if the overheating had caused a head gasket to fail. However, the biggest problem is not the centrifugal water pump- the biggest problem is the thermostat, a valve that controls the circulation of the coolant through the engine. While a thermostat can work flawlessly for years, they cannot be trusted: even new thermostats can fail without warning, and cause fatal overheating.”

“The point of all this is to prevent having to demonstrate your skill as a bush mechanic; you can remove a failed thermostat but since the rate of coolant circulation determines the overall efficiency of the cooling system, you might find that the low engine speeds in off-road driving does not circulate the coolant fast enough, which almost invariably leads to overheating. Thus, it makes sense to remove the single biggest cause of engine cooling problems and replace it with an electronically controlled variable speed water pump and its associated circulation control mechanism.”

“It may be possible to repair most things in the bush, but the truth is that it is better not to: a serious break down in the bush is not the same as having that same breakdown in the urban environment. For instance, temporarily fixing a leaking radiator hose with duct tape might not be a problem when the nearest workshop is only minutes away; repairing that same hose with duct tape when you are hundreds of kms from any sort of help is something else altogether because the duct tape might not hold, or you might not have the water to keep filling the radiator. Always remember that the best bush mechanics are those that do not suffer breakdowns, because they spend time and money on properly maintaining their 4WD vehicles.”


“One of the most common off-road problems is getting holes in radiators: it can happen to anyone at almost any time, so what do you do when this happens? Well, depending on the size of the hole, you can do several things”:

Radiator sealant:

“It is always a good idea to have some form of radiator sealant in your emergency supplies: some are better than others but most form a permanent seal in small perforations, say, not bigger than the size of a match stick. However, all radiator sealants require that you follow the instructions on the packaging, and remember never to remove the radiator or expansion tank caps when the system is hot and under pressure. Wait for the pressure to dissipate and follow the instructions on the pack; the leak should stop within a few minutes of introducing the sealant, but if it does not, do not keep adding sealant because you might block something else, especially if you use one of the dry, powder-type sealants.”

Radiator hoses:

“There is no reliable way to repair a burst radiator hose. Duct tape may last for a few minutes, but generally speaking, only old and partially perished radiator hoses cause problems. Of course, serious overheating could split even a new radiator hose, but then you should not blame the hose. As I mentioned earlier, radiator hoses are relatively cheap, and you only have yourself to blame if you are stuck in the middle of the Western Desert in Egypt because you did not replace your radiator hoses before you left on your trip.”

Radiator cap:

Radiator- and expansion tank caps wear out over time; they lose their ability to keep the pressure in the cooling system contained, which is their primary purpose. The last place you want to discover that you are losing coolant through a defective radiator or expansion tank cap is in the hinterland of Africa. The chances of finding a replacement are virtually zero, and if you do not have a spare in your emergency kit, you are in trouble. Simply replacing your radiator or expansion tank cap once a year is the easiest and most effective way of preventing coolant loss, and the major problems that could result if you lose too much coolant, especially in the parts of Africa where the temperature can reach 500 Celsius before ten a.m.

How to seal a radiator core:

“If the leak does not stop, you may have to cut out the core tubes that were damaged. To do this you may have to remove the radiator, but since you have a manual in your emergency kit, it should not be much of a problem. Once you have the radiator out of the vehicle, taking care to let it cool down first before removing it, you can cut through the soft vanes between the damaged core tubes with a sharp blade. Next, you use a sharp nosed pliers to crimp the ends of the cut core tubes before you fold them back on themselves two or three times. This will seal the cut tubes, but it will also reduce the efficiency of the radiator because there are now fewer tubes through which coolant can flow. However, cutting through even eight or ten tubes should not be too much of an issue if you remember not to let the engine labour under big throttle openings in low gears.”

“Once you have reinstalled the radiator, you can add some sealant just to be sure the repair is water tight, but always follow the instructions in the manual when you replace the coolant, since some cooling systems have to be purged of all the air that may have entered the system. Not all cooling systems are self-purging, so be absolute certain you follow the directions in the manual.”

“Of course, if you have an automatic transmission and you have to remove the radiator from the vehicle, you may have a problem because some transmissions use the radiator to cool down the transmission fluid. Removing these fluid lines can cause significant fluid loss, so make sure you have a plan to prevent this before you remove any pipes. There is no practical way to eliminate some fluid loss, but you can reduce the amount by having some plugged pieces of rubber hose to slip over the ends of the fluid lines, so have your mechanic make you some of these sleeves to keep in your emergency kit.”

“Also, remember that any fluid that does escape cannot be used again, even if you managed to catch it in a clean container. You have no way to be sure that no dust or other solid particulate matter did not get into the fluid, which if you used it in your transmission will definitely ruin it beyond repair. Just discard all spilled fluid, but not into the environment, keep it in a container until you can dispose of it safely.”

Misfires and power loss problems

“Modern engines, petrol and diesel, are very prone to developing misfires and rough running issues. There are many possible causes for this, and all of them have to do with the ridiculous complexity of the electronic systems that regulate them.”

“However, there are some simple tests you can perform in the bush, and it is important that you know all of them. Bush mechanics is not as complicated as it looks; given the relatively few things that can be repaired in the bush, it is now easier to find a problem, even if it cannot always be fixed. Diesel engines are generally less complex than petrol engines, so let us look at some of the things that you can do on a diesel engine that has lost power or is misfiring:

Water contamination of fuel

“More often than not, the diesel fuel you get in most of Africa is of dubious quality. I have personally found diesel with more than 20% of dissolved water in it, while the maximum allowable limit in the rest of the world is 5-7%, so this is by far the most common cause of misfiring and power loss issues on diesel engines, and even more so if you use biodiesel. Biodiesel that conforms to the ASTM standard has several advantages over petroleum diesel, but it does not always conform to this standard. Biodiesel and other alternative fuels does not form part of this lecture, however, there will be a lecture on this subject in the near future, so book for it as soon as you can.”

“While there are fool proof ways to detect water in diesel, such as various pastes and sensors, dissolved water will not always precipitate out of the fuel but there are many additives on the market that will “bond” the water molecules to the fuel. This makes it possible for the water to pass through the system, into the combustion chamber where, depending on the amount of dissolved water, it is sometimes converted in hydrogen under the extreme heat and pressure, and combusted with the diesel.”

“However, all the water that has precipitated out of the fuel should be drained off at least once every day, especially when you are in equatorial Africa, where it can rain every day for weeks on end during the monsoon season.” Water vapor in the atmosphere enters the fuel system through the filler cap and condenses on the walls of the filler pipe and tank. Most of this water may precipitate out and collect on the bottom of the tank, from where it is pumped through the system. However, since water is heavier than diesel, it will collect in the bottom of the water traps, which is sometimes incorporated into the fuel filter; some 4WD’s however, have separate water traps, so make sure you know where they are on your 4×4, and check and drain them at least every day.”

“Using water-contaminated diesel for long periods damages both the diesel pump and the injectors, so test your fuel regularly, and use appropriate measures to either drain off the water, or use additives to bond the water to the fuel so it can pass out of the system.”

Hard, or non-starting conditions

“A diesel engine that is in good condition and on which all systems are working properly, should always start within three revolutions, regardless of whether it is hot or cold. If it does not, bush mechanics can fix some of the reasons, while others require the services of a specialized workshop, so let us look at the most common reasons why a diesel engine could be hard or difficult to start”:

Loss of compression:

“Diesel engines depend on compression for the ignition of the air/fuel mixture; however, it is extremely unlikely that your engine will have lost its compression overnight, especially since you had been servicing it regularly. The loss of compression is usually a long, gradual process that gives you a lot of advance warning, and that is why I told you earlier to have the compression of your engine checked regularly. A compression loss of less than 10% will cause your engine not to start, but modern diesel engines are very robust, and if you have trouble starting yours, the problem is much more likely to be something else.”

Glow plugs:

“Like for instance the glow plugs. When a diesel engine is cold, such as after it had been parked overnight, the glow plugs supply additional heat energy to assist with the initial start up. Once the engine has started, the glow plugs will maintain this heat energy until the engine has reached a predefined temperature, after which the electronics will switch them off until the engine again cools down to a point below this predefined temperature.”

“Glow plugs have a finite service life, and they must be replaced in accordance with the service schedule of your particular 4WD. However, if you have an older model and you do all your servicing and maintenance yourself make a particular point of it to replace the glow plugs every 60-70 thousand kms. Diesel engines will usually start with one failed glow plug but it will not start with two or more; but that is not all.”

“Continually cranking a diesel engine takes a lot out of a starter motor as it is, but by continually cranking it, you allow the injectors to spray fuel into the cylinders with every revolution. Since this fuel cannot ignite, it builds up in the cylinders, increasing the compression even further, which places an even bigger strain on the starter motor. The fuel build-up also leads to a condition called “flooding”, which is an over-rich mixture that is impossible to ignite. Diesel engines should in any event never be cranked for more than five seconds at a time to prevent damage to the starter motor, and in many cases, the battery as well.”

“If you are in the middle of Africa, your overall weight is probably in the region of 3.5 tons, or even more, which is no joke to push start because you destroyed your starter motor. So just to be safe, replace your glow plugs at least every fourth service, and just to make doubly sure, keep a set of new glow plugs in your emergency kit. You never know when you, or someone else in your party, might need them.”

Fuses and relays:

“However, glow plugs are electrically operated, so make sure you know where the fuses, relays, and timers that control them are located. Many bush mechanics have needlessly taken apart entire engines when all they needed to do was to check the fuses. A fuse can blow for no reason at all, and a blown fuse might not necessarily indicate a problem of some kind, but if you suspect you might have an electrical problem, the first thing to do is to check all the fuses.”

“Your workshop manual will tell where all the fuse boxes and relay plates are, and since you have a good supply of replacement fuses and all the important relays in your emergency kit, you may find that all that is required is to replace a fuse. Nevertheless, make sure you have a circuit tester that plugs into the fuse holder: these gadgets measure the voltages and resistances in that specific circuit, and will show up any problems in that circuit.”

“If the circuit looks fine, replace the fuse anyway, since a discontinuity in a fuse might not always be visible or apparent. However, if a fuse continues to blow, there is some kind of problem with that circuit, so, never, ever, replace that fuse with one that has a higher rating than the one you are replacing. The individual wires in modern cars are no thicker than they need to be, so, they have no capacity to carry overloads. In practice, this means that wires might melt before the higher amperage fuse blows, which could very well destroy your 4WD by causing it to catch fire. If a fuse on a non-critical system keeps on blowing, do not force the issue, just do not replace the fuse until such time you can diagnose and repair the problem.”

Fuel/vacuum leaks:

“While fuel leaks that cause power loss problems because of fuel starvation might be obvious and usually not too much of a problem to fix, vacuum leaks in the fuel system are not always so obvious.”

“Petrol engines are fed by fuel that is displaced by a pump in or near the tank, but a diesel engine relies on fuel that is “sucked” through sometimes long lines, and an assortment of filters and water traps. Since the pump is located near the terminal end of the system, it makes sense that a vacuum leak could cause the fuel to stop flowing, and you might think that such a leak would be easy to spot because a leak that is big enough to let through air, will also let through liquid diesel. Well, this is not always the case.”

“You can have fuel starvation, especially during times of high demand, without any visible signs of fuel leaks. A sudden or unexpected loss of power because the engine does not get enough fuel could be dangerous, so it must be investigated and fixed as soon as the first symptoms appear, which could range from a slight power loss at high revolutions, to a sudden, and complete loss of power- so much so that the engine could cut out, even at average to low engine speeds.”

“The first thing to do when this happens is to check if there is fuel in the filter, and you do this by pushing down on the hand operated lift pump on top of the filter. This pump is used to prime the new filter after a filter replacement. The air in the filter is expelled through a bleeding nipple, or valve incorporated in the pump body, and if the area around the bleeding valve is dry, it could be that the pump itself has developed a leak past its seals, which creates an air bubble in the filter. In practice, an air space in the filter acts as a valve that cuts off the fuel flow.”

“When you push down on the lift pump you should feel a distinct resistance; this will mean that the filter is full of diesel, but if there is no resistance, it means that the main pump has drained the filter to below the level of the built-in pick-up, and the filter now contains more air than diesel. It also means that the main pressure pump has used all the fuel available in the line from the filter to the pump, with the result that the pump and the lines leading to the injectors are now full of air.”

“Although problems with lift pumps are relatively common, even on new vehicles, they do not as rule fail catastrophically without warning; on older vehicles they give you lots of warning. The first sign of trouble is usually some difficulty in starting after the vehicle had been parked for a while, or if it starts, it may only run for a few seconds before cutting out, irrespective of the engine temperature. This hard starting is that because of the vacuum leak in the pump, the fuel in the filter siphons back to the tank, and depending on how long the engine had been switched off, as well as the length of the fuel line between the filter and the pressure pump, there might be enough fuel available to allow the engine to start and run for a while.”

“Another sign is the time it takes to prime a new filter: a lift pump that is in good condition should not need more than about a dozen strokes to prime a filter, however, as a lift pump gets older, it could take several dozen strokes to prime a filter.”

“There is only one remedy for this problem, and that is replacement of the lift pump with an original OEM part. There are many cheap replacements available, but remember that they are cheap for a reason; they are invariably substandard parts made in China, and you just cannot rely on any replacement parts made there. However, if you are in the middle of say, the White Desert in Egypt, and your lift pump fails catastrophically, you are in trouble.”

“As I said earlier, sudden catastrophic lift pump failures are rare, but they do happen, so what do you do when it happens to you? Well, for one thing you could try sealing the area around the pump shaft where it enters the pump body casting with some of the two-part epoxy you have in your emergency kit. Just remember to first clean off the dust and diesel residue before you apply the glue. Then you wait for an hour or so while it sets. Then you hope that the bond is tight, but any sort of bond is better than no bond at all. However, this sort of repair is temporary at best, since no glue known to man is resistant to the corrosive effect of petroleum-based fuels, but it should get you to a repair facility where repairs that are more permanent might be possible.”

“Nonetheless, the down side of using adhesives is the fact that you cannot use the lift pump to prime the filter. Therefore, assuming that you have syringes in your first-aid kit, you can use one to fill the filter through the bleeding nipple. If you do not have syringes, you will have to unscrew the filter, fill it with diesel, and screw it back on. Whatever method you use, and assuming you have replaced and tightened the bleeding nipple the vehicle should start. It might take some cranking though, but if it does not start in ten seconds or so, remove the bleeding nipple, or the filter and fill the filter again. If the engine starts but dies soon after, just repeat the process until it idles without misfiring. This will tell you that the air in the system has been purged, but it will also tell you that you should have the problem seen to as soon as possible, as opposed as soon as practicable.”

“The failure of the lift pump is one of the most difficult problems to fix reliably in the bush, so many off-road drivers install electrically reciprocating fuel pumps to pressurize the filter, thus eliminating the possibility of vacuum leaks, but the problem with this is that these pumps have to run continuously on the one hand, and the fact that they are not approved by any vehicle manufacturer, on the other. To complicate things even further, these pumps can very often not handle the large flow demands of large capacity diesel engines, so instead of anticipating a problem, you might be installing one.”

“But a last word on lift pumps: they often last as long as the 4WD vehicle, and can work for years without any sort of problem, however, they can, and do fail, so, the best thing to do is to either replace yours at least every two years, or sooner if you use biodiesel, or keep a spare lift pump in your emergency kit. You might never need it, but on the other hand, you might need it at a time when finding a replacement could be impossible.”

Timing belts

“Of course, no lecture can cover all the possible causes of failures and breakdowns, but one last issue deserves mention, and that is timing belts.

“Timing belts should not be confused with the visible belts that drive the alternator and other equipment: from the perspective of vehicle manufacturers, timing belts are a cheap way to regulate the valve timing, and sometimes the fuel injection timing and water pump of an engine, but with that said, there is also a considerable weight difference between engines using timing belts and those using enclosed timing chains. However, from my perspective as a professional mechanic, these advantages do not outweigh the disadvantages of using timing belts on off-road vehicles”

“Timing belts and their tensioning devices are critical components: the correct functioning of the valve train and the diesel pressure pump depends on the belt being tensioned correctly, but not only that, for the belt to achieve its full useful life, it must be protected against oil contamination and the presence of dust, water, sand, and in the off-road context, the muddy water you often encounter in fast flowing deep water crossings.”

“The covers that enclose timing belts are never proofed against water, dust, sand, and mud, and the presence of any of these drastically reduces the life of a timing belt and its tensioner(s). Being made of nitrile rubber, modern timing belts are extremely tough under dust free conditions, but being exposed to the abrasive action of especially silicate dust and sand, a timing belt could fail at very much less than half its recommended, or claimed life.”

“The problem is largely one of economics, since everything to do with timing belts is expensive; from having it checked and possibly replaced before every time you go on an extended off-road trip, to recovering a 4×4 from the hinterland of Africa, because it suffered irreparable engine damage after the timing belt failed, to having to replace a failed timing belt in the bush, something all bush mechanics hate to do because it is such a difficult and mostly unnecessary job.”

“I am not suggesting that if your 4×4 has a timing belt, you should now replace it with one that uses an enclosed timing chain; all I am saying is that of all the possible causes of mechanical breakdowns, the condition of the timing belt is the one that is most often overlooked, when 4×4’s are prepared for long overland excursions. If you have an interference type engine, that is, one on which there is insufficient clearance between the valves and the pistons to allow the engine to rotate freely should the timing belt break, you should always replace the timing belt, its tensioner, and all the pulleys and sprockets it comes into contact with at no more than half the recommended replacement interval to prevent the possibility of a premature timing belt failure, and the destruction of your engine.”

“Of course, there are many engines that suffer no damage at all when a timing belt snaps, the so-called non-interference type engine, but even so, replacing a timing belt in the bush assuming you have one, is often a major undertaking, and one that should be avoided at all costs, mainly by replacing the timing belt as often as once a year and always by properly qualified mechanics who understand the need to get amongst other things, the timing belt tension right.”

“There is no point in replacing only the belt, since if you do a lot of off-road driving in dusty conditions, the sprockets and pulleys will also suffer premature wear, and a damaged sprocket will damage a new belt as much as the presence of sand will, so always replace all sprockets and pulleys as well.”

“OK, as far as bush mechanics is concerned, these issues are the main ones you are likely to have to deal with in the bush, but anything is possible and anything can happen, but provided you have been servicing your 4×4 regularly, there should be no other big things to worry about. Regular servicing and safety checks will have ensured that your battery cables and connections are tight and clean, and your brakes will also have been inspected for leaks and damage, so that should not be a problem. However, if you have a petrol engine, most of what we have been talking about applies to them as well, but petrol engines have their own problems, so let us look at some of the most commonly occurring issues”:

Bush mechanics and Petrol engines

“Petrol engines are more finicky and prone to electrical problems than diesel engines because they have more electrical components, and although modern engine management systems are generally reliable, they depend on about a dozen sensors and a small super computer to work.”

“The biggest problem with petrol engines, at least as far as bush mechanics is concerned, is the fact that unless a problem is obvious, such as a dead sparkplug, high tension lead, or an obvious fuel leak, it might be impossible to find a misfire or other problem that causes a loss of power. That is one side of the coin though; the other side has to do with the fact that even if a fault can be diagnosed, it is often impossible to fix because you might not have say, a spare ECU, or Engine Control Unit, or a mass airflow sensor.”

“Other problems that cannot be fixed unless you have spares are faulty or broken crank angle sensors as well as cam angle sensors. All modern fuel injected engines have these sensors and no engine can run without them since they generate the spark needed for ignition in the case of the crank angle sensor, and the regulation of the spark timing in the case of the cam angle sensor(s).”

“Although these sensors are usually very reliable and can work without trouble for the life of the vehicle, they are very easily damaged, which in the off-road environment is a distinct possibility. Any sort of problem with these sensors will illuminate the CHECK ENGINE light, but there are many other things that will do as well, such as a faulty catalytic converter or oxygen sensor, of which there can be more than one.”

“In short, there are hundreds of faults that will illuminate the CHECK ENGINE light, and all of them are cause for concern, especially if you are in the middle of say, the Sudan on your way to Egypt since you can never be sure what the actual problem is. Many faults that cause the CHECK ENGINE light to illuminate may not have an immediate negative effect on the performance or fuel economy of a petrol engine, but you can only determine that with the use of a good diagnostic computer.”

“When you are off-road, all warning lights on a 4WD should be taken seriously, since the problem could be any one of literally hundreds. Of course, you could buy a diagnostic computer and take it off-road with you, but the sheer number of parts you need to be able to fix whatever you find, makes the idea of a petrol engine in an expedition 4WD somewhat less than attractive.”

“This is why the vast majority of 4×4’s on long overland trips are diesels; they have a whole lot less electronics than petrol vehicles, however, modern CRD, or Common Rail Direct injection diesel engines are becoming just as complicated as any petrol engine, with the result that diesels have largely lost their proven reliability advantage.”

“These days, the choice of whether to get a diesel or petrol 4WD is largely a matter of personal choice, unless reliability and ease of maintenance is a big enough issue for you that you might want to pay the penalty in terms of fuel economy that an older, indirect injection diesel engine carries.”

“However, as I said before, petrol engines have their own particular problems, so let us look at the ones that are most likely to test your bush mechanics skills”:

Fuel system

“Although petrol engines are not quite as sensitive to compression loss as diesel engines, they are extremely sensitive to fluctuations in fuel pressure. Modern injection systems work at pressures of up to 200 bars, although the majority of petrol injection systems work at much lower pressures. However, fuel economy depends as much on the amount of fuel sprayed into the cylinder as the pattern of the fuel spray, and in efforts to make engines more fuel efficient, injector manufacturers have found ways to make the orifices in injectors smaller, in fact, the orifices in modern injectors are only a few microns in diameter, which makes it possible to achieve better atomization of the fuel, and hence better combustion and higher torque for less fuel used.”

High pressure fuel pump:

“This is all very well in situations where reasonably clean fuel is available, such as in most of Southern Africa, but as a general rule, the further north you go into Africa, the worse the quality of all fuel becomes, and although modern high pressure fuel pumps are protected by strainers to keep out the dirt found in fuel, these strainers are not fine-meshed enough to keep the finer solid matter out of the pump. The result of this is premature wear of the pump; imagine a pump the size of a beer can- this is size the pump that has to deliver fuel at up to 200 bars for years, and in something that small, there is not much room for wear.”

“Another problem is water contamination of petrol: combine the rate of premature mechanical wear caused by dirty fuel with the presence of rust caused by water contamination, and you will understand that no fuel pump can last indefinitely. Then there is the added problem of clogged fuel filters; most of the solid particulate matter in the fuel passes through the pump, where it is trapped by the filter. With the dirty fuel you get in Africa, it does not take very long for a fuel filter to become saturated with dirt and water, which places an even greater strain on the pump.”

“The first sign of high pressure fuel pump trouble is that you will start to hear it- a high-pitched whining sound, when the engine is running. A healthy pump is silent, so, when you hear the pump, the damage has already been done. From this point, the pump cannot deliver the required fuel pressure, with the result that fuel consumption will start to increase, because you now have to use larger throttle openings to achieve the same power output. This is because the fuel does not vaporize as effectively as before because of the lower pressures and the fuel management system will try to compensate by increasing the injection duration to more than the generally accepted maximum of around 6 milliseconds for the majority of engines under normal operating conditions.”

“There are hundreds of factors involved in delivering the correct amount of fuel to a cylinder at the right time, and all of them demand the correct fuel pressure, so, if one morning you start hearing the fuel pump on your 4×4 whine, and you are say, in the middle of Morocco, thousands of kms away from a replacement pump, what do you do? Well, for one, you will wish you had a spare high pressure pump and a couple of filters.”

“A noisy fuel pump could last for hundreds or even a few thousand kms, but then again, it might not. There is just no way of telling how long a damaged fuel pump will last, so the only thing you can really do is dig out your workshop manual, and replace the fuel pump with the spare you brought- there is no other remedy. Stripping out a fuel tank to replace a fuel pump in 500 C temperatures is no laughing matter, but neither is the couple of thousand Rand it takes every year to replace a perfectly good fuel pump just to be sure you do not break down in the bush thousands of kms away from any sort of help or assistance.”

“Off-roading through Africa is largely a matter of economics in the sense that you have to weigh the chances of breaking down against how much you are willing to spend to prevent you breaking down, but since you cannot drive without a working fuel pump, the choice should not be a difficult one to make.”

Fuel pressure regulator:

“At this point you may well ask how the working pressure in the fuel system is maintained, since as some of you may know, petrol injectors do not have return lines with which to return excess fuel to the tank. Well, it works with a pressure regulator that is connected directly to the fuel rail in most cases, but there are a few instances of it being part of the pump assembly in the tank. Although failure of this regulator is relatively rare, it does happen, and when it does, your 4×4 dies because this pressure regulator is a critical item without which the engine cannot run.

“One of two things can happen: the fuel regulator can stick in the closed position, in which case the pressure build-up can burst fuel lines or even the filter, and although the fuel pressure as an operating parameter is as a rule monitored by the onboard diagnostic system, the fuel pressure regulator is not. In practical terms, this means that if the CHECK ENGINE light illuminates because of excessive fuel pressure, you may not be aware that the pressure regulator is stuck closed. Even a diagnostic computer will only list the regulator as a possible cause of the increase in fuel consumption, black exhaust smoke, or the fact that the engine just died.”

“Similarly, if the fuel pressure regulator sticks in the open position, such as during a time when the fuel demand drops, you might end up with not enough pressure in the system to keep the engine running because the fuel pressure needs to overcome a preset spring tension in the injectors to enable them to work. Although part of this spring tension is overcome by the action of a small solenoid, the spring tension is required to prevent the injector leaking fuel into the manifold when the engine is not running. To make this a little clearer, let me put it this way: the pressure in the fuel system is not constant. Although the volume of fuel delivered by the pump is relatively small, more than 98% of it is returned to the tank via the pressure regulator, which is a simple spring operated valve.”

“ The reasons for the high return rate are firstly to ensure that enough fuel is available to supply the injectors at all times, but more importantly, to prevent the fuel in the fuel rail from forming vapour locks through heat transfer from the engine to fuel rail, which is very often bolted directly onto the engine block. Thus, by having a large rate of flow through the fuel rail, the excess fuel in the rail is returned to the tank before it has had the time to heat up to the point where it can vaporize.”

“One of the reasons the high working pressures of modern fuel injection systems are possible is because of the fact that petrol is relatively incompressible. However, when a vapour lock occurs, the liquid petrol turns into a rapidly expanding gas bubble, which pushes back against the fuel flow, and can thus prevent the further flow of fuel because the gas bubble is highly compressible, and while it may be expanding, its compressibility largely cancels out the rate of flow of the petrol.”

“The problem with all of this is the fact that there are many faults that can turn on the CHECK ENGINE light and many of them can cause the engine to cut out, and no matter how well developed your bush mechanics skills are, there is no immediate way of telling one problem apart from any other without a diagnostic computer. There are ways to test if a fuel pressure regulator is defective, but none of them are easy since it mimics the symptoms of other fuel related problems, such as a failing fuel pump, or a clogged-up fuel filter.”

How to trace fuel pressure regulator problems safely

“It has been seen that bush mechanics literally take entire 4×4’s apart in the bush while skipping around the actual problem, so, if you suspect a fuel related problem, the first thing to do is to let the engine cool down completely, and disconnect the battery(ies) before you undo any fuel lines. The residual pressure in the fuel system can take hours to dissipate and if you start undoing fuel lines while the engine is hot, the resulting fuel spray does not take much to ignite, so only work on the fuel system when the engine is cold and there are no ignition sources.”

“There is no reliable way to estimate fuel pressure: the only way to be sure you have the required pressure is to use a proper fuel system pressure gauge, but since you will be unlikely to have one, use your workshop manual to locate the fuel rail, and the fuel feed line that connects to it. Next, undo this line, taking great care not to lose any seals or copper washers, and stick the fuel line into an empty plastic cold drink bottle (or similar) to prevent fuel spraying all over the engine when you crank it.”

“Your workshop manual will tell you whether you have to crank the engine to get a fuel flow, or only to switch on the ignition, but whatever you have to do, there should be a very strong jet of fuel coming from the fuel line, indicating that the pump is working fine and that the filter is not clogged. If this is the case, reconnect the fuel line and again using your manual, locate the pressure regulator, and remove the fuel line leading from it.”

“Since you will have lengths of fuel line in your emergency kit, connect a long enough length of it to the regulator outlet to allow you to direct any spills away from the engine, and stick the other end into the same plastic bottle you used before. If after establishing a fuel flow the rate of flow is largely the same as the one you got before, it means that there is a good chance the regulator is stuck open, or partially open. If on the other hand there is no or very little flow, the regulator is stuck closed, or blocked by the accumulation of year’s worth of rust and gunk.”

“Either way, you are in trouble if you do not have a spare regulator, since the defective one you have cannot be repaired. It is a factory-sealed unit and any attempt to open it will destroy it; not that it matters much because it does not work anyway. Fortunately, this kind of problem does not happen very often, but if it does happen to you, you are in serious trouble. There is no way to run your engine without it, and you can go the length of Africa north of the Zambezi river without finding a replacement, so, the thing to do is to carry a spare, even though you might never need it.”

“Apart from the fuel filter, there are no user serviceable parts in the fuel systems of modern 4WD vehicles, but not only that, some items, like the pressure regulator, is mostly overlooked or ignored during routine servicing or maintenance operations, despite the fact that an engine cannot run without it. Off-road driving in Africa is tough enough without having to worry about breakdowns, and as I said before, the best bush mechanics are those whose vehicles never break down because they spend time and money on their maintenance. Bush mechanics, or in this sense, fixing major, preventable breakdowns in the bush is no laughing matter either, so no matter what anybody says, prevention is always better than cure so always carry the spares you cannot do without, even if you never need them.”

Mass airflow meter

“Another issue you might encounter is a malfunctioning mass airflow meter. This is a sensor that measures the amount or volume, and temperature, of the intake air and together with the throttle setting, helps to determine the amount of fuel needed to be injected, but not only that, based on the information supplied by the mass airflow sensor, the ECU, or Engine Control Unit, will determine whether to advance or retard the ignition timing, alter the valve timing on engines with variable valve timing, or even to change gears on automatics.”

A defective mass airflow meter can mimic the symptoms of other conditions, such as low compression, low fuel pressure, low engine vacuum on some engines, and even over advanced- or retarded ignition timing. This can make it very difficult to find the actual problem, but if your CHECK ENGINE light is lit up, and you have any of these symptoms, the first thing to do is to get out your workshop manual and locate the mass airflow meter.”

“Next with the engine running, disconnect the plug-in connector from the body of the meter, but be very careful not to break any wires: although the voltages on these wires are very low, you might find it difficult, or even impossible to repair a broken wire here. At any rate, disconnect the mass airflow meter and see if the symptoms are still there; let it idle and then rev it up a few times. If there is no change in anything, for instance, the engine is still idling erratically, very high, or not at all, or if it will not pick up revs, the problem lies with the mass airflow meter. If on the other hand, something, anything changes when the wiring is disconnected, it means that the mass airflow meter is functioning correctly, and the proof lies in the fact that the engine behaves differently with the wiring disconnected.”

“It is possible to clean the inside of a mass airflow meter, but it is very easy to destroy the actual measuring mechanism, so never touch anything inside it. The measuring mechanism is often nothing more than a very delicate heated platinum wire or plate, and it works by measuring the amount of energy needed to keep it at a constant temperature while air is sucked past it, so don’t touch it.”

“Fortunately, most issues with mass airflow sensors only involve the deposition of oil and dust particles on the wire element; particles that interfere with the effective transfer of heat, so, nine times out of ten, just cleaning it will restore it to full functionality. However, effective cleaning requires that you remove the entire assembly from the inlet tract, but since you have a workshop manual, it should not be a problem, but always use a cleaner that is specially formulated for the purpose, because the platinum element in most mass airflow meters have special coatings on them to protect them, and using the wrong cleaner could possibly remove this coating and damage the element itself. Just follow the instructions for reinstallation, and you should be on your way again in less than 30 minutes.”


“There are a great many causes of misfires, which range from leaking engine valves, to leaking inlet manifolds and vacuum lines, to defective injectors, to blown head gaskets, to water in the fuel, to defective spark plugs and/or high tension leads. However, if the engine temperature is normal, it is very unlikely (but not impossible) to be a blown head gasket, and if the misfire started some time after you last added fuel, or if you have not been driving in rain, it is unlikely to be water in the fuel.”

Spark plugs and high tension leads:

“So, assuming you did not blow a head gasket, and there is no water in the fuel, the first thing to do is to check all the spark plugs and high tension leads, or as they are also known, the plug wires. If the engine is hot, park under a tree, or other shade, and allow the engine to cool down for at least 2-3 hours. This is firstly because you might seriously burn yourself on a hot engine, and secondly, because attempting to remove a sparkplug from a hot engine could strip the threads out of an aluminium cylinder head, and if this happens, you are in serious trouble because there is no way to fix this in the bush.”

“Also, do not attempt to pull a high tension lead off a sparkplug while the engine is running; you could break the very delicate conductor, but more importantly, because if you get it wrong, the up to 40 000 volts or more running through the lead could kill you. Rather wait for the engine to cool down, and remove all the spark plugs one at a time, to prevent you losing track of which lead goes where, which could cause you to get the firing order wrong, which in turn could damage the engine.”

“The electrodes on sparkplugs that are in good condition have a light grey or beige colour, and no damage to the porcelain parts; other colours and conditions tell different stories, for instance, if a plug has a reddish colour, it could indicate coolant seepage past the head gasket, or the presence of certain performance boosting additives in the fuel. Very large gaps between the electrodes could be due to length of service or the presence of various contaminants to the fuel, but as a general rule, the sparkplug that is causing the problem is the one that differs significantly from the others in appearance.”

“A sparkplug that is wet, but otherwise not damaged or that does not have a large gap between the electrodes can be assumed to be defective. Similarly, sparkplugs that are encrusted with thick, hard grey or brown deposits are working at less than peak efficiency but the source of the encrustations should be investigated at the earliest opportunity. Sparkplugs that have black, powdery deposits on them indicate an over fueling problem which could be due to low compression or faulty injectors. Finally, sparkplugs that are covered in oil or thick carbon deposits indicate mechanical problems, such as broken or worn piston rings, oil seeping past the seals on the valve stems, or even a cracked or broken piston.”

“If the sparkplugs are not wet with fuel or oil, but there are noticeable differences in their appearance, replace them all with the spares you have in your emergency kit, paying close attention to the setting of the electrode gaps and tightening procedures in the workshop manual. However, the gaps on some sparkplugs, such as platinum and some multi-spark plugs should never be reset: consult your workshop manual if you are unsure because these sparkplugs are preset during manufacture and changing the gaps could damage the ignition system because of the change in resistance, and always use only the spark plugs recommended for your 4×4 by the manufacturer. Using the wrong spark plugs lead to reduced performance, increased fuel consumption, and possible damage to the electronics of your 4×4.”

High tension leads:

“If the misfire or rough running persists, the problem is then likely to be defective or malfunctioning high tension leads. It is always a good idea to have at least one or two spare leads that are specific to your 4×4. If the misfire is still present after changing the sparkplugs, replace the high tension leads one by one, checking if the problem is still there after each replacement. Nine times out of ten, you will resolve the problem in this way, unless of course the problem still persists and you have multiple ignition coils.”

Ignition coils:

“it is impractical to carry spares for every single electrical component on a modern 4WD, but many bush mechanics carry at least a spare set of sparkplugs, a set of high tension leads, and a spare ignition coil if the vehicle uses a single coil that feeds spark to all the cylinders. However, some systems use individual coils for each cylinder, known as pencil coils, so if you have such a system, carry at least two of these coils as well. Therefore, if the misfire persists after having changed the sparkplugs and the high-tension leads, and you have an engine with individual coils, unplug, and reconnect the low-tension wires from each coil in succession while the engine is idling. You will notice a distinct difference in the way the engine idles when you unplug coils that work; on a coil that does not work, there will be no difference in the way the engine idles. Once you have identified the defective coil, simply replace it with one of the spares you have in your emergency kit, making sure you do not dislodge other wires and connections in the process, because replacing a pencil coil could sometimes require you to strip off other components.”

Fuel injectors:

“If the misfire still persists, use your workshop manual to locate the plugs that connect to each injector, and with the engine idling, unplug and reconnect each in succession. Just like with the ignition coils, unplugging the defective injector will make no difference in how the engine idles, however, replacing a fuel injector sometimes require you to strip off several major components, but by following the step-by-step instructions in the workshop manual, you should not encounter any major difficulties, assuming of course you have a spare injector. Nevertheless, before you start stripping the engine, first check that there is power to the injector: simply attach a test light to earth and with the other end, briefly touch both connectors in the plug in succession.”

“One point in the plug is a negative, and will not light up the test light, but the other is a positive and if you touch that, and you have good earth connection, the bulb in the test light will flash on and off like an indicator light while the engine is cranking. Do not however, short out, or bridge the points in the injector plug with anything; this will cause a major short circuit and you could damage the entire system, but if your test light confirms there is power up to the injector, the injector is proven to be defective and if you have a spare, you have to replace it, but only by following the instructions in the manual to prevent damage to other components.”

“Replacing an injector can be a major undertaking so make sure you have some sort of container on hand to hold the various nuts, bolts, clamps and other fasteners in one place for fast and easy reassembly. A last word on injectors though; it makes good sense to have at least one spare new injector in your emergency kit. An injector may be expensive and you may never need it, but the fact of the matter is that injectors do fail and there is no way any amount of bush mechanics experience can repair a petrol injector. If it fails, the only remedy is replacement, no matter how inconvenient or time consuming it may be.”

“Think about it this way- you may have spent more than your house is worth on financing your overland trip through Africa from Cape Town to Cairo, so the price of one or two fuel injectors is not going to make that much difference to the overall capital cost of the trip.”

Vacuum leaks:

“If despite your best efforts to locate and fix the misfire, it still persists, the next step is to check the vacuum circuit. Petrol engines can sometimes have several dozen vacuum points that regulate a host of systems and sub-systems. However, finding all these connection points and tracing the vacuum lines that connect them is always a difficult and time-consuming affair, so use the vacuum diagram in the manual to be sure you can find and check them all.”

“Modern engine vacuum systems can be very complex but you are very unlikely to encounter vacuum problems on new 4WD vehicles. Problems caused by vacuum leaks range from running rough, to general misfiring, to hard starting, to erratic or high/low idling, to not idling at all, to uncontrollable jerking and surging on some German-made engines, and last but not least, extremely heavy fuel consumption.”

“Vacuum lines harden and split with age, so this type of problem is more commonly found on older 4WD vehicles, although it can happen on new engines as well. Vacuum leaks can often be heard as a persistent “sucking” sound but not always though. It can sometimes be a high-pitched whistling sound, especially if the leak is somewhere in the inlet tract, where the passing air causes a gasket to vibrate.”

“Fixing a vacuum leak is very often as easy as cutting the end off a vacuum tube and reattaching it, but it can also be much more complicated than that, so, if the vehicle is drivable, rather get to the nearest repair facility or camp site where it is easier to trace the problem and make proper, reliable repairs.”

“Nonetheless, to fix a vacuum leak you first have to find it, something that is frequently much easier said than done. One way to find a leak is to spray some penetrating or water repellent spray over everything that looks like vacuum tubes or fittings while the engine is idling. If you are lucky, the spray will temporarily seal the leak while it is sucked in, so you will notice a difference in the way the engine idles. If you find the vacuum leak this way, well and good, but if you do not, you may have to trace and physically check every joint and connection, something that could take hours, if not days.”

However, this is also the time you will be sorry you did not spend the time and money to keep your 4×4 in peak condition since in all likelihood, regular diagnostic checks will have identified an incipient vacuum related issue, which should have been repaired before you left on your overland trip through Africa.”

“One last thing about vacuum systems and the trouble they can cause: not all vacuum systems are critical, at least not in the sense that you will be stranded if they developed leaks. For instance, if you suspect a vacuum leak but the brakes, air operated diff locks, and the turbo works fine, and if the engine starts and the 4WD can be driven comfortably and safely, do not start taking the engine apart to try and find the leak. You might never find it and it might not even be a vacuum leak: it could be an electronic problem that is beyond the ability of even the most skilled and knowledgeable bush mechanic to diagnose and repair, especially if the affected 4×4 has engaged, or is in “limp mode”.

Limp mode

“On newer 4WD’s, whether petrol or diesel, almost all operating systems are controlled by micro-processors that rely on signals from various sensors, such as those controlling the ignition, fuel supply and regulation, transmission in the case of automatics, turbo boost, and others. To keep the several thousand signals that control a modern 4WD synchronized on a millisecond basis, the ECU, or Electronic Control Unit, which is a sort of clearing station for all the electronic activity, is programmed to first analyze the signals it receives to determine if they fall within strictly defined parameters.”

“Assuming all the sensors to be performing within limits, the ECU uses these signals to regulate the smooth and efficient working of the engine and transmission. However, it sometimes happens that a sensor becomes defective, and unless the affected sensor fails completely and causes the engine to shut down, it may continue to generate signals, but in an erratic or intermittent fashion.”

Default programming:

“Nevertheless, the ECU is also programmed to recognize erratic signals as well as those that fall outside the accepted parameters, and as soon as it receives this type of signal it will immediately and automatically revert to “limp mode”, which is a set of operating instructions that amount to a “survival mode” to protect the engine and transmission against damage that could result from a defective sensor.”
“For instance, if something in the ignition system goes wrong, the ECU in limp mode may retard the timing and limit throttle inputs to prevent the timing from over advancing, which causes premature ignition and can burn holes in the pistons. The ignition timing on EFI engines is always set to maximum advance by the ECU to ensure maximum performance under all conditions, however, the timing needs to be retarded under certain conditions, such as large throttle openings at low engine speeds because under these conditions, over advanced timing causes premature ignition, rough running, and in some cases engine overheating.”
“Premature ignition causes a knocking sound, which is the sound of an uncontrolled detonation of the air/fuel mixture in the cylinders, so the engine uses a type of microphone, called a knock sensor, to identify these knocking sounds, and when they are detected, the ECU will retard the ignition timing until the knocking just disappears. In this manner, the timing is continually adjusted to the optimal setting for any conceivable condition. Therefore, to use our example, if anything should go wrong in the ignition system that does not shut the engine off, the ECU will go into limp mode to enable you to drive to a safe spot or a repair facility, whichever is the closest.”
“Of course, due to the nature of the “survival mode” programming, you will be limited to very low speeds, and you may have very limited throttle control, In addition, if you have an automatic transmission, the system will also limit you to only one or two gears, usually first and second, and if you are lucky, reverse gear as well.”

Limp mode and off-road driving:

“This is all very well if you live near a choice of repair centers, but things are a little different in the off-road environment; in fact, off-road driving can sometimes cause a modern 4×4 to go into limp mode at very inconvenient moments, such as during deep-water crossings, because some wiring got wet. When this happens, the ECU can usually- but not always- be reset to normal values by switching off the engine and restarting it again after a few seconds.”
However, if the ECU went into limp mode because of a genuine malfunction in a sensor or system, it will generate a fault code before illuminating the CHECK ENGINE and sometimes other warning lights, but you will usually know you are in limp mode when the CHECK ENGINE light either flashes or turns red from the normal yellow or amber colour. Not that it helps much to know you are in limp mode, because you need a diagnostic computer to fine the failed sensor or system.”
If the ECU does not reset, you are in trouble: you don’t know what the problem is, but even if you did, you probably do not have the spare parts to fix it, and that is why this type of situation is without doubt the single most compelling reason why you should never go on long off-road trips by yourself.”
“You might think that replacing the ECU will resolve the issue, and it might, but the Rand prices of ECU’s can run into several multiples of ten thousand, however, if you can afford it, well and good, but remember that if the fault persists, the replacement ECU will go into limp mode as well, so you are still stuck.”
“In Africa north of the Zambezi river (and sometimes south of it too), there are no tow trucks to rescue you, so what is the solution if none of the other drivers in the party are willing to tow you to the nearest campsite or workshop?” You cannot really blame them; your fully loaded 4×4 is probably twice as heavy as the maximum towing capacity of any 4×4 in your party, so your choices are rather limited.”

Carry enough electrical spares:

“Prevention is always better than cure, but if you add another adage, the one that says knowledge is power, you can largely eliminate the possibility of being stuck in the hinterland of Africa, sometimes a thousand kms or more from any sort of assistance. Being a professional mechanic, I appreciate and understand how tough and durable modern 4WD vehicles are; however, I also understand how easily they can break down, especially the electronics.”
“There are widely differing opinions on what spares to carry, but I have more than 60 kg’s of electrical spares in my own 4×4. Admittedly, I have only had to use one knock sensor from my stock, but if I did not have it available two years ago, I would probably still be stranded in Mauretania, waiting for a spare to arrive from South Africa.”

Bush mechanics in Africa

4x4-africa-road-repairs“As was said before, off-road driving in Africa is tough enough without having to worry about what spares to carry and what not to carry. This is not so much of an issue in South Africa where there are thousands of repair facilities, or even in most of Southern Africa, where you can arrange spares and servicing without too much trouble, but Africa north of Zimbabwe is another kettle of fish altogether.”
“I would be irresponsible to tell you to trust to luck, just because you had been servicing your 4×4 after every trip; it would also be stupid to tell you to carry hundreds of replacement parts if you do not know their function or how to replace them, or even if you do not know in what respect a part might be defective.”
“Bush mechanics is a skill learned over many years, so the best advice I can offer you is to familiarize yourself with the workings of your 4×4. Study all the various systems in your workshop manual until you have at least a good working knowledge of what parts do what, as well as basic fault finding procedures. Going about finding a problem the wrong way can sometimes cause more trouble than the original problem, so learn as much as you can about your particular 4×4, and all of its systems.”
“No one becomes a good, or even mediocre at bush mechanics overnight, and nor should anyone have to, but the next lecture in this series is about compiling a checklist for off-road driving, which will among other things, deal with what to take along and what to leave so that if a problem does occur, and you need to rely on your bush mechanics skills, you will be likely to have at hand what you need to fix the problem.”

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