Have you ever seen a car stopped on the road, giving off white smoke and accelerating by itself in front of the driver's disbelief? If yes, it is very likely that have seen a diesel engine in «auto-combustion». The term is not a happy one, but we are open to suggestions (the English call it runaway engine). Forward…
What is it?
Simply put, self-combustion in Diesel engines happens when, due to a mechanical failure (which in 90% of cases happens in the turbo), the oil enters the intake and the engine starts to burn the oil as if it were diesel.As this input of fuel (read oil) into the engine is not controlled, the engine accelerates on its own to maximum speed until the oil runs out.
They can turn off the car, stop accelerating and even take the key out of the ignition!, that nothing will work and the engine will continue at maximum rpm until:
- Run out of oil;
- The engine seizes up;
- The engine starts.
Result? A very high repair cost. New engine!
So how can I stop the engine?
Most people don't know how to act in a situation where the engine is auto-combusting (see attached videos). The first (and most logical) reaction is to turn the key and turn off the car. But in the case of diesel engines this action has no consequences. The burning of diesel, unlike gasoline, does not depend on ignition.
As long as there is air and oil to burn, the engine will continue at full speed until it catches or breaks. See below:
First advice: don't be nervous. The priority must be to stop safely. You only have two to three minutes (estimate) to try to put the advice we're going to give into practice.
When they have come to a stop, shift into the highest gear (fifth or sixth), apply the handbrake, apply the full brake and release the clutch pedal. They must release the clutch pedal quickly and decisively — if you do it gently, it is possible that the clutch will overheat and the engine will continue to run.
If the engine stopped, congratulations! They've just saved a few thousand euros and they'll just have to change the turbo — yes, it's an expensive component, but it's still cheaper than a complete engine.
What if the car is automatic?
If the car is automatic, it will be difficult to stop the engine. Crouch down, grab your knees and cry. Okay, calm down… it's difficult, but it's not impossible! All they need to do is cut off the air supply to the engine. Without oxygen there is no combustion.
They can do this by covering the inlet with a cloth, or by firing a CO2 fire extinguisher into that location. With any luck, they should have been able to stop the engine. Now don't turn it on again, otherwise the cycle starts again.
The best way to avoid auto-combustion is to act preventively and treat your car engine well — check out some of our advice. Careful maintenance and correct use will save you a lot of “disadvantages”, believe me.
Finally, another example of “autocombustion”. Possibly the most epic breakdown of all: