I've been trying to solve a cooling system problem over the past couple of weeks and need some advice. This is for my '88 944 non-turbo.

The problem is overheating, especially in some of the bad traffic jams here in Atlanta. The temp guage was going over the second mark (100 deg C), so we had to park the car and let things cool down, and let traffic dissipate until we could get home. Fortunately the weather has turned cooler. The fans nerver switched to high speed, so I was thinking that something was wrong with the thermofan switch. In any case, I pulled the connector from the thermofan switch and tested the fan relay according to the procedure in the Clark's Garage manual. Relay checks OK - fans working at low and high speeds. So I went ahead and replaced the thermofan switch. That must not have been the problem because I'm still seeing the temperature climb up to that second mark and just hang there. We drove the 944 up to the Petit LeMans yesterday at Road Atlanta and the car ran OK - temp below the 100C mark, but not where it should be on a cool fall day on the freeway and taking it easy. On the way home, the guage hit the 100C mark again and pretty much stayed just below it. So I thought that maybe the system needed bleeding, and this morning I started the car and let it warm up, letting the bleed valve open making sure that no air bubbles were coming out (with heater on). Again, the temperature guage climbed past the first mark (80 deg C) and was getting close to the second and the fans had not come on at all. Also, even though the bleed valve was open and coolant was coming out, there was no change in the level of the reservior. I touched the radiator and it was warm, but not hot at all. So I'm thinking that the thermostat is not opening all the way. The fans finally did come on at low speed, but the temp guage was at the second mark. The fans had just come on low, and theoretically should have been ready to switch to high speed if I understand how the system works.

Since the temp guage reading comes from the block, but the thermofan switch is in the radiator, it's possible that a partially closed thermostat might keep the two parts of the cooling system (block, radiator) at different temps, so I don't hear the high speed fans coming on, but see the temp climbing past 100degC. It might be opening enough that the block gets some coolant flow, but keeps the engine over normal operating temp.

So -- seems like I should replace the thermostat. Anything I might be missing here?

 

Thats where I would start, then move to fun things such as the radiator itself.

 

Yeah, it was the thermostat. But OH MY GOD - that snap ring. It was an easy job except for that bit.