CAR CLINIC | Identify and prevent the 5 most common causes of car fires

Few things are more pitiful than the sight of the burnt-out hulk of a car at the side of the road.  

Even the mute evidence in the form of a blackened patch on the tar with the tell-tale debris strewn about is enough to conjure up a picture of the horror of a car fire.  

The unfortunate fact, however, is that in the most cases the owner is to blame.  

Here are some of the common causes of car fires:  

1: Petrol leaks  

Caused by rotten, cracked or poorly clamped fuel lines. If there's enough petrol vapour around, you only need the tiniest spark to start a fire, and tiny sparks there will be in an engine compartment. The ones at the spark plug electrodes ignite the internal combustion, but the ones at the commutator of a working starter motor, for instance, may start a devastating external combustion. Diesel fuel, in liquid form at least, is much less flammable than petrol. It will not usually be ignited by a spark. Diesel vapour, however, can explode if the conditions are right – people who have to do welding on fuel tanks are very aware of this.

2: Dodgy electrical wiring  

A short-circuit or bad earth connection, especially in the heavy-current, unfused starter circuit, can generate astounding heat within a matter of seconds, enough to ignite plastic insulation or flammable liquids. Even something like hydraulic fluid will burn if the temperature goes high enough. Besides the danger of excessive heat, the sparks from a bad connection that is arcing also pose a risk in the presence of petrol vapours.

3: Overheating engines  

Overheating can cause flammable liquids to expand beyond their design limits and drip onto a hot exhaust manifold, for instance, where they may burst into flames. Defective oil seals or porous gaskets can allow gear oil to leak out, with a similar result, even when the engine isn't overheating.

4: Catalytic converters  

These get very hot in operation. If a vehicle with a catalytic converter is parked over dry grass after a fast run, the grass can catch fire if it touches the car. With the approach of winter when the highveld will have lots of dry grass, remember instances have been recorded where cars have burned out in this way.

5: Crashes   

This is one fire risk that we cannot prevent by good maintenance. Despite advances in bodywork design and materials, a severe impact, coming from the wrong direction, can rupture fuel lines (or burst a petrol tank)  and cause sparks at the same time, creating a lethal combination. A readily accessible fire extinguisher is worth its weight in gold in such an event. A car fire, once it has started, burns with fearsome ferocity. The moral of the story is to investigate any petrol smell immediately, look after the electrical wiring, watch out for oil leaks, and invest in a fire extinguisher. If you are a passenger in a car that catches on fire, don't hang around in the hope it will die down. The opposite is more likely to happen when the fire reaches fuel lines and combustible upholstery and insulation materials. The only exception would be if you can grab a fire extinguisher within seconds and know how to use it. Reaction time is critical in such cases. Other than that, the operating principle remains: cars can be replaced, lives not.