Ogge

Hi! After changing the thermostat on my 944 -83 it started overheating (well, it runs up to max on temperature gauge and then fans turn on and it goes down to the middle).
I've read on clarks garage that this probably is due to me either having purchased a new thermostat to my old waterpump or that I have a new style waterpump and I bought an old style thermostat.
How do I know whether I have a new style waterpump (do they look different?) and what parts do I need to change?

- Oscar

Wabi

This video does a good job explaining the differences, hope it helps!

jderimig

When you say runs to max do you mean it touches the max zone or goes well into it? If it get close to touching it then fans turn on that is normal (or within tolerance). What is was the temperature rating of the thermostat you installed? 83C?

Ogge

It goes to the max line and then the fans turn on (sometimes it might go like 1mm above before the fans actually do some cooling). It didn't do this before changing the thermostat which is why I'm concerned. The new thermostat is indeed a 83C.

jderimig

After I changed my waterpump mine seemed to do the same. Fans seem to be kicking on a little later than I remembered. I got concerned and replaced my thermostat last fall, The one that came out was an 81C, new one was 83C. Both boiling water test passed.

I have a "new style" water pump and the seal depth was the old 4.5mm not 7.5mm of the post 89 pumps. There is actually 2 versions of the new style pumps depending on what turbo core the rebuilder used.

If the fans kick on that means that the thermostats are opening correctly. I would bleed really well. Took me about 3 tries and each time the fan kick-on temp dropped a little bit. Mine kicks on just below that max line, but sometimes it touches it.

How did you bleed the system? Front of the car raised?

Ogge

I was very thorough when bleeding the system, hade the front raised and ran it for a long time, letting it cool off several times etc. Should barely be any air in the system.

jderimig

If you have the 7.5mm waterpump and did not use the thick seal ring and steel spacer ring, then the thermostat will not close off the bypass path when t-stat opens. This reduces coolant flow to the radiator prolonging the time when the fans kick on. This will allow the engine block to get a little warmer.

This is something I am going to check myself once the weather gets warmer here.