Clint's 944

Quick background....I was going down the road and I happened to notice the car was overheating!!! I mean the gauge about jumped out of the cluster!! So I immediately turned the car off and coasted to a stop. I popped the hood and I noticed that the fans were not running. So I tried turning on the a/c with engine off and slowly but surely the temp. began to drop.

My question: When I bypassed the thermo switch the fan comes on in both speeds. So, would be safe to assume that my thermo switch is bad and the cause of my overheating? I would have thought traveling at 60 MPH would have kept the car somewhat cool, is this wrong?

i murdered hitler

i wouldnt think your fan would turn on at 60 mph. how was your coolant level?

Clint's 944

My coolant level hasn't changed...and the top radiator has pressure in it when warm. My thoughts exactly about the fans...I'm reaching for answers. Coolant is flowing so that eliminates the water pump, right? Gauge seems to be working fine as it rose/dropped steadily instead of jumping. Themostat should be fine as water is flowing. So, where else can I look?
-Thanks for the response....

KuHL 951

It's hard to believe that the car would overheat at freeway speed...fan or no fan. Sounds like your flow rate through the system has taken a nose dive. Water pump could be going south or your thermostat is stuck in a partial open position. The fans wouldn't run at freeway speeds but it does sound like the thermoswitch is gone. 1st guess, faulty thermostat, barely open.

Tom M'Guinn

At freeway speeds, you should not overheat with or without the fans. I second the thermostat guess.

Clint's 944

OK...update. I think I know what happened. I cleaned the engine yesterday and I read in the archives that some people had strange things happen with temp gauge after cleaning the engine. I just went out for a drive and everything is back to normal!!! Whew...I just ordered new hoses, expansion tank, front bushings for everything I could see, low temp thermo switch and misc seals and interior parts. I was not looking fornward to anymore expenses this week!!!
Thanks for the help....and thanks rennlist for the archives!!!

TheMAXX

Are you sure that it was overheating and it wasn’t just the gauge (or sensor) acting up. If it was overheating it most likely would have been spitting out coolant all over the place. The expansion tank cap opens up when the pressure gets too high.

It does sound like your thermal switch may be bad. But if the cooling system isn’t full and there isn’t any coolant at the thermal switch then it may not turn on.