I agree with Init2winit. Normally, a thermostat problem is not intermittent. The thermostat only does 2 things EVER; open and close. When they go bad, most of them stay closed and thereby causing overheating problems. Some of the newer "safety" thermostats are designed to stay open when they fail, but I highly doubt that if you've never had it changed before that this is the kind that's in there.


I would look at the fan(s) closely. It's an easy check. They either work or they don't. Like Init2winit said, if they do work, then you have a coolant flow issue somewhere. Have you checked to be sure you haven't blown a head gasket? Although most of the time that too will overheat all the time and not intermittent.

Do you have any leaks? I know my car had a tiny tiny leak thru a hose that was resting up against my my downpipe. I kept losing coolant and couldn't find why since I park it over carpet every night. When it would get low, the temp would creep higher than normal. Once the leak was fixed, it's never gotten past where it'd always stayed. Remember that the coolant goes into a closed system. In other words, if you're having to continously add more and more, it's likely to be leaking out somewhere. Put a big piece of cardboard under the car and see if you have any leaking fluids.

Hope it helps.