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Q: Car overheating and there is no cabin heat while at idle.

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Car overheats when foot is off gas. When I stop at a light or park the car, the engine gets hot (temperature needle is at 'H' mark. Also, when I stop, I lose heat inside the car. It starts blowing cool air. As soon as I step on the gas, hot air starts to come through the vents again. The cars temperature gauge will top out for example, when parked after I've been driving for 15 minutes. If I rev the engine, the temperature gauge will instantly drop down.

I have had a repair shop replace the water pump, thermostat, bleed air out of the cooling system, do a chemical test for leaking head. The heat sensor was also replaced because the fan wasn't kicking on while idling. But still the car is overheating. I can drive the car on the highway for over an hour and the temperature gauge needle sits around the 3/4 mark between middle and top (H). As soon as I get off the highway the temperature gauge maxes out. There is no sign of coolant loss either.

My car has 100000 miles.
My car has an automatic transmission.

Hi there. Check the radiator to the vehicle. It seems that the cooling system is working, but the radiator is restricting the coolant flow. This is why when you step on the gas pedal the coolant temperature drops. I recommend flushing the radiator or even replacing the radiator if its still not cooling after a flush. Your heat in the vents will get warm when there is coolant flowing and with a plugged radiator there is no flowing coolant to the heater core. If you need further assistance with your cooling system, then seek out a professional, such as one from Your Mechanic, to help you.

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