Thermostat problem?

Even though I'm new, I searched around and could not find a conclusive answer to my problem.

I've got an '02 325i, with 140k miles on it. Just today, I was driving it, and the temperature gauge was creeping up, ultimately getting hot enough for the red light to come on. In the <100 feet that I kept driving in order to have a safe place to pull over, the needle went back to normal. The needle did not stay on hot for very long, making me thing that it is something other that the engine over heating.

From what I have read from searching, worst case scenario its a head gasket if the coolant/oil is milky (which I have not checked yet; engine still hot) or it is a bad thermostat.

Any other opinions on the matter?

NO! DO NOT drive anymore before you do a cooling system overhaul. It could be a 4000 dollar mistake to do so!

Originally Posted by scarede46er

NO! DO NOT drive anymore before you do a cooling system overhaul. It could be a 4000 dollar mistake to do so!

+1 You don't want to roll the dice with an aged cooling system and car starting to overheat.

Most likely it is your thermostat, but could also be a failing water pump, or air in the system. Just do the overhaul and be done with it.

Thermostats usually fail in the open position, resulting in your engine running cold, not hot. 1st things 1st: have you checked your coolant level when it's cold? Do you see evidence of any leaks? If everything seems OK, go through the coolant system bleeding procedure to eliminate any air in your system. Keep a close eye on your temp gauge, as you really do not want to overheat your engine. Good luck.

A few days ago, the yellow coolant light came on, so I topped it off, but when I checked it after this recent indecent (when cold, of course), it was quite low. I have not checked the system for any other evidence of a leak, but would any thing other than a leak cause the coolant level to drop in such a short period of time? I'm not in a position to do a DIY, even though I would prefer to, but I guess I'm really just trying to figure out exactly what I am getting into before having it taken to the shop.

Use the OBC hidden functions to pull up the engine temperature reading and then drive the car slowly and stay close to home. Normal temp is no higher than 95 C. Gauge is notorously useless. If overheating really takes place, you need to fully explore the thermostat, WP, radiator, etc. Best way to go on an aging car with no service history is to replace all the critical cooling system parts. Not expensive, especially if you DIY.

Questons?