Overheating problem

[Eric]

I took the 325 to an auto-x today, and after every run, I noticed the old thing would overheat a bit. it wouldn't go into the red, but it wouldn't stay in the middle. After the run i drove it around to keep airflow through the radiator. Once i got above 40mph or so the temp would dip below 1/2 way. Usually the temp needle is glued to the center of the guage, so i think the thermostat is bad.

After the first run, i just turned the car off and went to the booth to check out my time. after about 10 minutes i went back to the car to see it taking a piss! all of the coolant in the overflow tank had gone out the expansion tube, and somewhere else under the intake manifold.

the usual crowd of car guy Dr.'s came in for some diagnosis, but nobody could find a loose hose or anything wrong. So i went and bought some lunch and some anti-freeze. i filled her up with the engine running, and she didn't overflow again.

I'm thinking shutting the engine off while that hot is why it overflowed, and the cooldown laps did help a bit. but i'm still worried about the car overheating. a 1:25 run in 2nd gear is a lot different that 10 minutes at the nurburgring. I'm affraid that i'll puke a motor 1/2 way through it's first lap out there!

So, anybody have a guess what's wrong?

edit: BTW, i was the second fastest of the day :)

[jlevie]

While the thermostat or a clogged cooling system is a possibility, my first guess would be that you have a bad fan clutch. AutoX speeds are generally low enough that the engine fan is important and if the fan clutch has failed in the usual manner the fan is moving little air.

I suspect that your cool down wasn't long enough and the stored heat in the engine was never removed and caused the coolant to boil. Or it could be that your radiator cap is bad.

You can test the fan clutch by dragging a rolled up newspaper against the blade tips whilt the engine is idling. It should be easy to stop the fan when the engine and radiator are cold and difficult to stop the fan when both are at operating temperature.