Car Overheats At Idle

My car seems to want to run much hotter, and sometimes to the point of overheating and actually boiling over mostly when I am sitting still or at idle.

When I get the car moving it seems to cool down and there are no problems. I have flushed the radiator and replaced the thermostat, but the problem continues. Can this be a blown head gasket problem?

Hey Alan,

My first thought is that you have a bad electric cooling fan motor. These small electric motors are in front of or in some cases behind the radiator in the front of the vehicle.

These fans will cycle on and off as the engine temperature dictates pulling air across the radiator to cool down the engine when at slow or idle speeds. I would guess one of these fans is not operating, and thus the overheating problem.

Your car might have just one fan or it might have two fans, and one is generally for the cooling system and one is a “condenser” fan that helps improve air flow across the air conditioner condenser. When that fan fails, the air conditioning performance at idle or slow speeds is greatly reduced.

Both fans operate via a separate relay and the radiator cooling fan uses a thermal switch inside the radiator to determine when the fan motor should come on and off. Here is a picture of a vehicle with a radiator cooling fan and an air conditioner condenser fan motor.

Andi birthday 033

Austin Davis

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Austin Davis, consumer car repair advocate. "Hi there! I love to help people solve their car repair problems and I hope my site was helpful to you today. Thank you for stopping by."