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Q: Car overheating/fluctuating on temperature.

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When I'm driving my car with the heat on(i work graveyard shift, so it's cold out), everything will be fine, until my RPM's drop below 1,500. Once that happens, the heat slowly goes away(getting colder and colder) and the temp needle on my temp gauge(Engine temp?) starts to go higher and higher. Once I start going above 1,500 RPM's(whether revving the engine, or accelerating/driving at higher speeds)the heat returns from the vents, and the needle goes down. Furthermore, once I get to work in the morning, after driving about half an hour(mostly freeway at 60mph), I can pop my hood, and my radiator cap is cold as can be. I have replaced the Thermostat already, no real change. I didn't bleed the coolant, but have burped it once(this resolved the issue for about a week). The car does the same thing at stop signs/red lights/freeway traffic overheating when RPM's aren't up. Temp Sensor?

My car has 168000 miles.
My car has an automatic transmission.

Hello, thank you for writing in. There are several other components that can cause a malfunction with the cooling system. You are in the right realm of thinking however, and there is likely a bad circulation of coolant or air in the system. Sensors can be an issue and may need to be looked at eventually. Air typically works its way out after a while, and burping the system again can’t hurt it. The water pump is driven by the engine’s drive belts. If the engine decreases in power the water pump will have less power. Typically the engine will compensate for this, however if the pump is failing, there is only so much compensation that can be done. The water pump should be the next component to look into. For more help diagnosing the issue, contact our service department.

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