Ask the Mechanic: Why does my diesel engine stop and start itself whenever I brake?

Hello Paul, I recently bought a 2016 Toyota Hilux 2.8 diesel double cab. When I stop in traffic, the engine goes off and starts again once I release the brake. This happens even after the engine has been running for hours, which raises the question of whether the engine needs to cool down after a long time running. Perhaps ‘modern’ turbo diesel engines do not need to cool, or was it just a myth in the first place?


Hello Johnson, the symptom you have described on your Toyota Hilux 2,8D seems to be the normal function of the Automatic Start Stop (ASS) technology on your vehicle. This feature will automatically switch off the engine when you brake for a while at traffic stops, junctions or in traffic jams. The car will start itself when you release the brake pedal or gently tap the accelerator in different models.

This innovation is common in many post-2016 vehicles and is designed to reduce emissions as well as save fuel. Modern diesel engines do not need long warm-up or cool-down time as the older ones did. Modern engines have advanced cooling systems which work more efficiently to cool down the turbo.

Nevertheless, it is a good habit to let the engine idle for a minute or so when you stop after driving fast. This will allow the turbo to slow down before you stop and cut off the oil pressure. This will prevent premature wear of the turbo bearings.


Hello Paul, I bought a car from a dealer in July 2017 but in March 2019, the car broke down due to a serious engine problem. Should the dealer take all responsibility?


Hello Steven, when you buy a car from the dealer and it develops a serious engine problem after two years, your ability to hold the dealer responsible for compensation will be determined by the following; terms in the purchase agreement, the laws governing purchase agreements, whether the car was brand new and had a three-year warranty that can only be honoured if the dealer you bought from is an appointed manufacturer representative. If you bought a used car, did it come with a limited warranty of say one or two months?

The quote or purchase agreement of a brand new car must spell out the warranty period such as three years and what areas of the car are covered. Worldwide, car manufacturer representatives can easily provide warranty cover if the engine failure is found to be a result of manufacturer fault, not user fault or misuse. In some rare situations, engine or component failure could be a result of a known build-related defect announced in a bulletin for a product recall. You can go online and find existing product recalls for warranty replacement.

Here, the manufacturer acknowledges an engine or component failure due to build fault or poor quality. The manufacturer will arrange for free replacement of faulty components or engines (in extreme cases) through the appointed dealer.  In your case, you should have agreed on how long the warranty would be and what components it covered. It is rare for used car dealers to provide a warranty because they are selling used cars whose component life span they may not know. 

Warranty periods usually come with terms and conditions such as the appointed dealer will have to service your car engine with the right fluids and filters. Taking the car to another garage for service or repair may nullify any sort of warranty depending on the agreed terms. Should you fail to comply with the terms of this agreement, the dealer is free to withdraw the warranty. In Uganda, there is a law for sales agreements which your lawyer can help to explain. Seek an audience with the car dealer to seek clarification.

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