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Q: Thermostat leaking coolant

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I need the thermostat in my car replaced as it is leaking coolant. When I turn on the heat or AC, it blows a cloud of misty grey smoke. The car leaks coolant even when idling.

Hello, the coolant leak will need to be repaired sooner rather than later to avoid overheating and engine damage. I would say that you have a leaking heater core based on a coolant leak and a mist from the vents. The new thermostat is probably not an issue, but the coolant leaks will still need to be repaired. Have a mechanic from YourMechanic come out and pressure test the cooling system to detect the leak and make the proper repair. If the heater core is leaking there is a chance that the instrument panel must be removed for access to the heater box.

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