I recently drove a friend’s car (a 2002 Toyota Yaris) that overheated due to a leaking water pump. I noticed that, when the engine overheated, it eventually cut out and refused to start. It could only be restarted once the engine cooled down and after we topped up the cooling system. Please could you explain this functionality and if all Toyota engines would behave like this under similar circumstances?
MAHIN CHAUHAN, Bulawayo
Answer: Most new vehicles have engine-protection strategies programmed into their ECUs. Our technical editor Nicol Louw worked on a Ford Transit project on which the maximum engine torque would be reduced due to increases in engine temperature until the motor would only be allowed to idle. This is to protect the engine from by damage due to overheating. Depending on the software supplier (Bosch, Continental, Delphi and others) for a specific model, we assume that a company like Toyota has one engine-protection policy for its entire range. Some manufacturers measure the coolant temperature, whereas others measure the cylinder head (metal) temperature. The latter is a safer option because, even if all the coolant is lost, the engine-temperature reading would still be accurate.