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Q: Can a bad thermostat cause me to have to keep putting coolant in my car?

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My car runs hot sometimes. The temperature guage will go all the way up and come back down to normal. Also I smell the coolant sometimes when I get out my car and I never had that problem before. On some days it runs hot but most days it is fine.

My car has 161000 miles.
My car has an automatic transmission.

A: Hi, thanks for writing in. The thermostat i...

Hi, thanks for writing in. The thermostat in the engine cooling system is a valve that opens and closes as engine temperature fluctuates. The purpose of the valve is to keep the engine operating temperature at a relatively constant, optimal level of roughly 200 degrees. Keeping it at that temperature maximizes the efficiency of the engine while preventing damage from too high a temperature. If the thermostat is malfunctioning, for example sticking, that could cause the car to overheat. The odor of coolant is probably due to very hot coolant overflowing into the reservoir, and perhaps even out of the reservoir, on those occasions when the engine is operating too hot. Overheating is not good for the engine. If severe, it can cause quite a bit of damage actually, including things like a warped cylinder head or engine block. If you are having to add coolant more than once or twice a year, you have a leak somewhere in the cooling system. If the engine is overheating, the best to do is get the cause identified and repaired. YourMechanic specializes in just that sort of diagnostic and would be glad to help you with this issue so that you can get your car repaired and running normally. Our technicians can come directly to your home or office to inspect your car for you.

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