Categories: Motoring

How to ruin a car without trying

Common sense will help to ensure years of trouble-free motoring. Lack of it can have disastrous results, says Jake Venter.

The owner’s manuals of modern cars contain much useful advice, as well as many warnings.

If you ignore these, or don’t know about them, you can damage your car in a matter of minutes. Some of the following warnings will be found in manuals; others will not.

Wrong fuel
Filling a fuel tank with the incorrect fuel type (petrol for a diesel-engined car or vice versa) is a far more common error than one would think.

Statistics are not available in South Africa, but in the UK it has been calculated that this mistake takes place on average every three-and-a-half minutes!

If petrol gets into a diesel tank, the amount of damage will depend on how long the engine has been running. If the engine has not been started, there won’t be any damage but all the fuel should nonetheless be drained off.

If the engine has been running, it should be stopped immediately and the car towed to a workshop. The problem is that diesel fuel is a lubricant, but petrol is exactly the opposite.

If diesel fuel gets into a petrol tank, the engine will struggle to start and run badly, but damage is only likely to occur if the engine runs for some time.

Parking on grass
Never park on dry grass or other combustible material. Modern exhaust systems include catalytic converters that operate at temperatures high enough to set grass alight.

Exhaust systems have heat shields in place, but their effectiveness is nullified if the grass is long enough to penetrate past the shield. The problem is magnified by the low ground clearance on many cars.

Watch the following YouTube video: Parking or driving on dry grass.

4×4 trails
If you have been off-roading, check your vehicle thoroughly before returning home. Most importantly, reinflate your tyres if you have lowered the pressure; failing to do so risks having a blowout.

If the vehicle was driven through water, the paper air cleaner element should be checked for signs of dampness and even removed temporarily to ensure that the engine will get enough air.

Dampness can close up the pores of the filter, resulting in a rich fuel mixture and increased consumption in a petrol engine, and possible severe overheating in a turbo-diesel.

Overfilling the sump
Some pump attendants try to get you to “add one pint” of oil when showing you the dipstick reading.

A 500ml can should be added only if the oil level is near the low mark, otherwise you could end up with too much oil in the sump. In a petrol engine, this is merely a nuisance – it may cause smoking and oil leaks – but in a diesel engine, it can be catastrophic.

If the oil level is so high that oil is sucked into the intake manifold, the engine will speed up – out of control and pouring smoke – until something breaks.

The only way to stop it is to block the air intake with cloth or thick paper. Watch the following YouTube video: Insane runaway diesel.

Not using the handbrake
Not long ago, somebody I know parked his car facing uphill on a very slight slope. He engaged first gear but did not employ the handbrake. After a while, the slowly diminishing pressure on top of the pistons caused the car to start moving rearwards down the hill.

After about 100m, the car finally bumped up against a tree, sustaining damage. But it was the engine that suffered most. Because it had been forced to rotate backwards, the timing chain had jumped a tooth.

This caused the valves to strike the pistons, causing considerable damage.

Jake Venter is a journalist and a retired engineer and mathematician. Email him at

Published by
Caxton Magazines

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