CAR CLINIC | How to make sure your car is ready for holiday travel

The AA list of common causes of vehicle breakdowns makes interesting reading. A flat battery is high on the list, but probably not on a long summer trip, though a dysfunctional charging system can ruin batteries at any time. Lost keys or keys locked in the car also feature prominently. Most car keys have a microchip as protection against car theft and this makes it harder to replace lost keys.

The best precaution is to hide a spare set of keys in a secure, accessible, yet out of sight place on the vehicle. Use a small, well-sealed tin to hold the keys. Paint it black and attach it hidden somewhere with a blob of epoxy adhesive. For good measure put a strong permanent magnet inside the tin and stick it on a steel surface. This will hold the tin in place even if the adhesive cracks.

Other frequent causes of car trouble on long trips include flat tyres and running out of fuel. The latter is not as unlikely as it may sound, because fuel gauges can be faulty for many reasons. A gauge might, for example, get stuck, lulling you into a false sense of complacency even as the tank is running dry. Always monitor the gauge and be wary of a gauge that doesn't drop as it should during a trip.

In a country with high summer temperatures, such as South Africa, the biggest hazard on a long holiday trip is probably engine overheating. 

Modern cars have more efficient cooling systems, unlike some cars in the 1940s and 1950s. In those days it was not uncommon for engine coolant (mostly just plain water, often unpressurised) to boil when climbing a mountain pass on a sweltering day. Motorists learned to take such events in their stride. The cast iron engines were tough enough to shrug it off. At worst the engine would cut out because a vapour lock prevented fuel being pumped to the carburettor. You had to let the car coast to a safe spot. But the engine would usually start again and run as sweetly as before if you let it cool down and top up the radiator.

Improved engine design and the widespread use of aluminium, a much better conductor of heat than cast iron, have relegated boiling engines to reminiscences of senior citizens. Nowadays cooling systems are sealed and pressurised. Putting liquid under pressure raises its boiling point. Additives in the coolant prevent freezing in winter and raise the boiling point.

Nevertheless, engines still overheat and the drawbacks of aluminium come to the fore: it expands about twice as much as cast iron when it heats up, and this, coupled to less rigidity than cast iron, means an aluminium cylinder head is prone to warping when overheating. A warped head almost always entails a blown head gasket and high cost of repair or, more likely, replacement.

So it is important to maintain a modern car's cooling system in tip-top condition. Serious overheating should never be allowed on an aluminium engine.

Here are some tips to prevent problems:

• The ratio of antifreeze (which doubles as corrosion inhibitor) to water should be kept at the prescribed level. On modern engines the coolant seldom needs topping up, but when it does, one should top up with the same mixture as the manufacturer's recommendation.
• Long-life antifreeze has a service life of five years or 200,000km, whichever comes first. This means five years — few people cover 200,000km in less than five years. It's important to adhere to this drain interval to prevent a build-up of sludge and a depletion of the chemical properties of the additives. On older vehicles with copper or brass radiators a traditional green antifreeze will provide better protection for lead-soldered radiator cores and end tanks.
• Frequent need to top up the expansion tank is cause for concern. It may be an external leak which can quickly become a gush of coolant onto the road. This could easily go undetected while driving, but will rapidly be followed by serious overheating unless the engine is switched off immediately. The other possibility is a leak into the engine through a failing head gasket. This sometimes shows up as white, condensing water vapour in the exhaust emission. Either way, disaster is looming.
• If the radiator fan fails to switch on when it should, overheating will occur in congested traffic where there is insufficient air flow through the radiator to provide cooling. Have an auto electrician fix the problem.
• Cooling-related components, such as hoses and the seal on the cap of the expansion tank, necessary to maintain pressure in the system, should be inspected regularly and replaced when necessary. Don't overlook the water pump which is sometimes hidden behind the cambelt cover. It will usually weep before starting to leak.

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