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Q: Engine switch off

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I was driving on motorway for about 4 hours and half when my engine got to warm when I was on trafic. The car switch off and I had to wait 20 min to start the car. It happen again but this time the engine was only on 80c degrees. Te next day when driving to work the car was running fine until I stopped on trafic lights, the car then switch the engine off but the temperature was only 80c. I had to wait 20 min to start the car again. The oil and the coolant levels are good. Can you say what might be the problem? If it is the CPS or the thermostat? Thanks Bruno

My car has 83000 miles.
My car has an automatic transmission.

Hey there, thanks for asking about your 2005 Smart Fortwo. When a car overheats in traffic, it’s a pretty sure sign your cooling fans are not working. You can test this by letting your car fully warm up and observing this at home. Depending on the weather, it will take sometime for it to fully warm. The first thing to watch for is the thermostat to open. You can know when it opens by feeling the upper radiator hose. It will be cold until the thermostat opens, at which time it will become hot. At this point, your car is still not warm enough to turn the radiator cooling fan on.

Make sure you watch your temperature gauge while you are doing all this. If the gauge gets hot and the upper radiator hose is still cold, it’s time to replace the thermostat. If the upper radiator hose and the gauge gets hot, but the radiator cooling fan does not turn on, the cooling fan operation will need to be diagnosed.

As for the dying, this seems to happen while you are at a stop. This indicates the overheating problem may have damaged a computer module. CPU’s are sensitive to heat. The first overheating event may have damaged the CPU or ignition module so that as soon as they begin to get hotter than they should, the module will quit working. This is a very common occurrence with electrical modules.

If you should need assistance, I recommend you have a certified technician from YourMechanic inspect why your car is overheating](https://www.yourmechanic.com/services/car-is-overheating-inspection).

Keep in mind, the damage to the module is already done. But it may not need replacement as long as the car doesn’t get hotter than it can handle; it may still last for the life of the car.

Good luck!

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