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Q: Had changed thermostat for heat. Had changed and now car overheats when idle.

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Bought the car in Apr 2016. Car has over 129000 miles on it. Drove perfectly fine. No problems. Car has a.c. But no heat. Changed the thermostat for heat and a week later the car starts to overheat when in idle. Took it to a mechanic to get it flushed. He said there was corrosion and needed a good flush. He also said that there might be air in my coolant system and he got rid of it.He managed to get the heat working and the car was driving fine for 2 days till I got on the highway and parked up to the gas station and I noticed the temperature went almost up to the red zone. Turned the car off and let it cool off. Drove back home and the temperature was normal and when I parked up again it raises up again.

My car has 136000 miles.
My car has an automatic transmission.

Hi There, It sounds like you may have some cooling fans that may not be working correctly. The coolant fans are triggered to come on at specific temperatures and controlled by a cooling fan relay. When this relay goes bad, this may cause the fans to come on intermittently, all the time or in some cases not at all. This is noticeable by an erratic temperature fluctuation, especially at idle speeds as you have described. I would recommend having a professional from YourMehcanic come to your location to diagnose and inspect your cooling system.

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