Before you depart on an overland journey, use your vehicle for several months, to run in any new parts properly. This will enable you to find any weaknesses and become acquainted with its handling and maintenance.

Give it a thorough overhaul before leaving. If you fit any extras, make sure that they are as strong as the original vehicle. For precise navigation, you should know how accurate your odometer is, for the tyres fitted: larger tyres, e.g. sand tyres, will have a longer rolling circumference. Fit a battery isolation switch: it could save your vehicle in a fire and is an excellent anti-theft device. (New models of these will allow enough power through, to run any necessary clocks and memory systems, when disconnected.)

Loading

Overloading is the largest single cause of broken-down vehicles and the easiest to avoid. Calculate your payload against the manufacturer's recommendation for the vehicle. Water is 1 kg per litre, fuel roughly 0.8 kg per litre, plus the weight of the container. Concentrate on the essentials and cut back on the luxuries. It could make all the difference between success and failure.

By using several identical vehicles travelling in convoy, you can minimise the weight of spares and tyres to be carried. The idea of using one large vehicle to carry fuel etc., accompanying several smaller, more agile vehicles, does not work out well in practice. The larger vehicle will often be heavily bogged down and the smaller vehicles will have difficulty towing it out, often damaging their drive train in the process. Also, the vast difference in general journey speed and the extra spares needed cause many problems, unless you are to have a static base camp.

For rough terrain, trailers are not advisable. They get stuck in sand, slip into ditches and overturn on bad tracks. Powered trailers have been known to overturn the prime vehicle. On corrugated tracks, trailer contents soon become so battered as to be unrecognisable. Trailers are impossible to manhandle in sand or mud, and make life difficult if you have to turn around in an awkward situation. They also reduce the efficiency of the front wheels' driving and put strain on the rear axle.

If you must take a trailer, make sure that it has the same wheels and tyres as the towing vehicle, that the hitch is the strong NATO type, and that the wiring loom is fixed above the chassis, where it will be protected.

Regular checks

Once in the field, check the chassis, springs, spring shackles and bushes, steering, bodywork, exhaust and tyres, every evening when you stop for the day. Every morning, when it is cool, check engine oil, battery electrolyte, tyre pressures and cooling water, and fill the fuel tank. Check transmission oils and hydraulic fluids at least every third day. In dusty areas, keep breather vents clear, on the axles, gearbox, and the fuel tank filler cap. Keep an eye on electrical cables for worn insulation, which could lead to a fire.

Make sure that you carry and use the correct oils and fluids in all systems. Deionising water crystals are easier to carry than distilled water, for batteries. Remember to lubricate door hinges, door locks, padlocks etc., and remember that in many deserts you need anti-freeze in the engine for night temperatures.

Brush all parts clear of sand or dust before working on them. When working under a vehicle, have a groundsheet to lie on and keep things clean, wear goggles to protect your eyes. A small vice fitted to a strong part of the vehicle will aid repairs. In scrub or insect country you'll need to brush down the radiator mesh regularly.

Punctures

Punctures are the most common problem in off-road travel. Rear wheel punctures often destroy the inner tube, so several spare inner tubes should be carried. Wherever possible, I prefer to repair punctures with a known good tube and get the punctured tube vulcanised properly, when I next visit a larger town. However, you should always carry a repair kit, in case you use all your inner tubes. Hot patch repair kits do not work well enough on the truck type inner tubes that are used in four-wheel drive vehicle tyres.

Michelin radial tyres have the advantage that their beads almost fall off the wheel rim when flat. If you cannot break a bead, try driving over it or using a jack and the weight of the vehicle. If the wheel has the rim on one side wider than the other, remove the tyre over the narrowest side, starting with both beads in the well of the wheel. Narrow tyre levers are more efficient than wide ones. Sweep out sand and grit, file off any sharp burrs on the wheel and put everything back together on a groundsheet, to stop any sand or grit getting in to cause further punctures.

When refitting the tyre, use liquid soap and water or bead lubricant and a Schrader valve tool to hold the inner tube valve in place. Start and finish refitting the tyre, by the valve. Pump the tyre up enough to refit the bead on the rim, then let it down again to release any twists in the inner tube. Then pump the tyre up again to rear tyre pressure. If the wheel has to be fitted on the front later, it is easy to let out some air.

Foot pumps have a short life in sand and are hard work. If your vehicle does not already have a compressor, then use a sparking plug socket fitting pump if you have a petrol engine, or a 12 volt electric compressor which can be used with either petrol or diesel engines. Keep all pumps clear of sand. When using electric compressors, keep the engine running at charging speed.

Damaged steel-braced radial tyres often have a sharp end of wire internally, causing further punctures. These should be cut down as short as is possible and the tyre then gaitered, using thicker truck inner tubes. The edges of the gaiter should be bevelled and the tyre must be at full pressure to stop the gaiter moving about. On paved roads, gaitered tyres behave like a buckled wheel, so they are dangerous. Most truck tyres (including Michelin XZY) can be re-cut when worn and these re-cuts are useful in areas of sharp stones or acacia thorns, where tyres damage easily. (These re-cuts are not legal on light vehicles in the UK.)

Wheel braces get overworked in off-road use, so also have a good socket or ring spanner available, to fit the wheel nuts. With a hot wheel after a puncture, you may need an extension tube on the wheel brace, to undo the wheel nuts; but do not retighten them this way or you will cause damage.

In soft sand, use a strong one-foot-square metal or wooden plate under the jack, when jacking up the vehicle. Two jacks, preferably including a high-lift jack, are often necessary in off-road conditions.

If your vehicle spare wheel is stored under the chassis, it can be difficult to get out, when you have a puncture off-road. Store it inside the vehicle or on the roof.

Fuel problems

Bad fuel is common; extra fuel filters are useful, and essential for diesel engines. The main problems are water and sediment. When things get bad, it is quicker long- term to drain the fuel tank, decant the fuel and clean it out. Always keep the wire mesh filter in the fuel filler in place. Do not let the fuel tank level fall too low, as this will produce water and sediment in the fuel lines. With a diesel engine, you may then have to bleed the system. If fuelling up from 40-gallon drums, give them time to settle and leave the bottom inch, which will often be water and grit.

If you have petrol in jerry cans in a hot, dry climate, always earth them to discharge any static electricity before opening, and earth the vehicle before touching jerry cans to the fuel filler pipe. Fuel starvation is often caused by dust blocking the breather hole in the fuel tank filler cap.

Electric fuel pumps are unreliable; carry a complete spare. For mechanical fuel pumps, carry a reconditioning kit. In hot countries or in low gear at altitude, mechanical fuel pumps on petrol engines often get hot and cause vapour lock. Wrap the pump in bandages and pour water onto it to cool it. If this is a constant problem, fit a plastic pipe from the windscreen washer system to the bandaged fuel pump and squirt it regularly.

Low-pressure fuel pipes can be repaired using epoxy resin adhesives, bound by self- vulcanising rubber tape. High-pressure injector pipes must be brazed or completely replaced. Carry spares of these and spare injectors.

Diesel engine problems are usually fuel or water, you should know how to bleed the system correctly. If this fails to correct the problem, check all fuel pipes and joints, fuel pump and filter seals, for leaks. Hairline cracks in the high-pressure injector pipes are hardest to find. Fuel tank leaks repair best with glass reinforced plastic kits.

Electrical problems

These are a constant problem with petrol engines. Carry a spare distributor cap, rotor arm, sparking plugs, points, condenser and coil; all tend to break up or short out in hot countries. Replace modern high-tension leads with the older copper-wire type and carry spares. Keep a constant check on sparking plugs and contact breaker points. If you are losing power, first check the gap and wear on the points. Spray all ignition components with silicone sealant to keep out dust and water.

Keep battery connections tight, clean and greased. Replace battery slip-on connections with clamp-on types. Keep battery plates covered with electrolyte, top up only with distilled water or deionised water. Batteries are best checked with a battery hydrometer. There are special instruments for checking the modern sealed- for-life batteries.

Alternators and batteries should be disconnected before performing any electrical arc welding on the vehicle. Never run the engine with the alternator or battery disconnected. Alternators are not as reliable as they should be. If the diodes are separate, carry spares; if not, carry a complete spare alternator. On some vehicles, the red charging warning light on the dashboard is part of the circuit, so carry spare bulbs for all lights. Make sure you carry spare fuses and fan belts.

Regularly check that batteries are well clamped down and that electrical wires are not frayed or passing over sharp edges. The risk of electrical fire due to shorting is very high on rough tracks.

Overturned vehicles

Given the nature of the terrain they cover, overturned vehicles are not unusual on expeditions. Normally it happens at such a slow speed that no one is injured, nor even windows broken. If this happens, your first action should be to make sure the engine has stopped and the battery is disconnected. Check for human injury, then completely unload the vehicle.

Once unloaded, vehicles can usually be righted easily using manpower, though a second vehicle or winch can make things easier, in the right conditions. Once the vehicle is righted, check for damage, sort out all oil levels and spilt battery acid, and any oil that may be in the intercooler (if fitted). Then turn the engine over several times with the sparking plugs or injectors removed, to clear the bores of oil above the pistons.

Short-wheelbase vehicles have a habit of breaking away or spinning on bends and corrugations, often turning over. So drive these vehicles with extra care.

Drowned vehicles

Make sure that the occupants are safe, rescue them first, then recover the vehicle to safe ground, where it will not obstruct other traffic. Empty the vehicle and allow it and all electrical components to drain and dry out. Check for water and silt in drum brakes, all oils and fluids, the air filter and the air inlet system, clear and clean as necessary. Water is heavier than oil, it sinks to the lowest point and can be drained at the drain plugs. If oil looks milky, it will have been emulsified by moving parts: wait several hours, drain off any free water and replace with new oils as soon as is possible.

Drowned engines

Note the 'caution' in 'Overturned vehicles' above.

With diesel engines, change the fuel filter and clean the sedimentor if fitted. Remove the sparking plugs or injectors and turn the engine over in short bursts with the starter motor. Continue until there is no sign of water in the cylinders. If there is sediment, strip the engine down. Refit all components and run the engine till warm; check for problems, especially for shorting out of electrical components - these could cause a fire. Stop the engine and recheck fuel filters for water, and drain or clean as necessary.

When you reach civilisation, have the vehicle hosed out with fresh water and replace all oils and fluids with new ones. With diesel engines, fully service the injector pump and injectors. If the vehicle drowned in sea water, have the complete wiring loom replaced and all electrical connections cleaned, or you will be plagued by minor electrical problems for evermore.

Extreme cold

Arctic temperatures are a very specialist situation. Vehicles are stored overnight in heated hangars. When in the field, engines are either left running or else have an electric engine heater, which is plugged into a mains power supply. Oils are either specialist or diluted to the maker's recommendations.

Petrol is the preferred fuel for lighter vehicles but, for heavier uses, diesel vehicles have heaters built into the fuel system and the fuel is diluted with petrol. All fuel is scrupulously inspected for water before being used. Batteries must be in tip-top condition, as they lose efficiency when cold.

General tips and improvisations