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Q: Truck over heats while idling

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I had my water pump and hoses changed out about 2 months ago, truck had not over heated since then. i was driving on the highway yesterday, and noticed when i got off the highway my truck was overheating. The temp got up to 240. Not sure what I could exactly be. Maybe the fan clutch??

My car has 220000 miles.
My car has an automatic transmission.

This can be caused by a number of things such as low coolant levels, a faulty thermostat, or a failing coolant fan switch. As you may know the coolant fan switch helps to maintain the proper coolant temperature by turning on and off at specific temperature thresholds. When this switch is not working properly, this can cause the fans to come on intermittently, all the time or sometimes not at all. When this happens you will notice a temperature spike and drop occasionally as the fan comes on and off.

When your thermostat is not working properly or is stuck closed, this will not allow the coolant to properly circulate through the engine, which may cause the engine temperature to fluctuate erratically or in some cases just remain hot. In your case, as you are driving down the highway and the wind blows through the radiator, this helps to cool things down that may not be otherwise cooled down properly. When your truck slows down to an idle and any of these components are otherwise not working properly, this may cause the heat to rise. I would suggest having an expert from Your Mechanic come to your location to diagnose your cooling system.

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