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Q: Coolant is leaking, but vehicle not overheating.

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I have to keep filling the coolant in my vehicle every week. I cannot see the leak and the vehicle does not overheat.

A: Hello, a coolant leak with no external leak...

Hello, a coolant leak with no external leaks leads me to believe you might have an internal leak at the head gasket. The first thing to do would be to check the oil and see if it looks like chocolate milk. If the oil looks ok, the next step would be to pressurize the coolant system, remove the spark plugs and see if coolant is entering into one of the cylinders. Unfortunately the coolant leak might also be temperature dependent and it may take some time to find it, some leak hot, some leak cold and some leak warm. To help, have you noticed that it might run a little rough at startup, like it has a misfire for a few seconds? If so, note the engine temperature and the amount of time the engine ran to get to this point. This information will help when pressurizing the cooling system and to determine which cylinder the head gasket is leaking into. You may need to enlist the aid of a mechanic to perform the above steps.

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