gruffalo

hi,

my 928 is apparently running a too low operating temperature, I suspect the coolant to be flowing through the radiator all the time, for some reason.

I boiled the thermostat on the kitchen stove today, and it opened the prescribed 8mm (according to the wsm). It appears to be functional (83 degree one)

Please check out the problem further here:

http://home.online.no/~maosme/bil/coolshark.htm

mm

Vilhuer

AFAIK all 928 engines should have seal inside. It's condition is probably one of the least known easy fixes for cooling system problems.

gruffalo

but I can not onderstand how the missing seal affects cooling. The thermostat fully closes the opening to the upper radiator hose! The seat is at the other end of the thermostat.

There is no such seal on an 81 euro according to PET, only on the 32v cars.

Or am I mistaken? If so, what is my part #?


mm

Dennis Wilson

Did you measure the movement on both plates/gates or the thermostat? As the top one opens, the botttom should close. full movement should be about 8mm. It appears the rod between the gates is bent on yours which would prevent the bottom gate from fully closing. That would actually make your engine run hottersince more coolant would be bypassing the radiator. The bent rod could also account for the slow warmup. Recommend you replace the thermostat.

Concerning the cool reading, have you checked the connectors at the temps sender to see if they are loose/corroded?

Dennis

gruffalo

well, I'll get a new thermostat and both seals. And from there on I'll be checking the gauge.

but my subjective impression is that the engine actually IS cool.

Are there any other plausible causes for this?

MM

Vilhuer

It's possible to install thermostat wrong way around so that smaller top plate points to the front. But this should cause overheating by blocking upper radiator hose so probably not same problem.

As you have quessed pourpose of inside seal is to close one of the water passages inside block. There is flow chematicks picture in some factory document what illustrates how liquid flows when thermostat is closed and open. It should explain why seal is needed on all engines. Just can't remember in what document that pic is.

Garth S

Everyone is correct - to a degree ( couldn't resist a bad pun ). There was no rear seal fitted to the 16v engines AFAIK. Maybe they can be retro-fitted, but I do not know if that is possible, or even a good idea.
The pump discharge is directed to the block via the rear passage until the engine warms sufficiently to open the thermostat. The rear plate 'seals' the rear passage while opening access to the rad - and redirecting flow.
An error that has been made (PO's only ) is installing the large O-ring behind the thermostat pellet. If this were the case, the rear flange would never reach the back opening to effect a seal: unusual cooling performance would result, as it would with the bent or binding shaft mentioned.
When in doubt, try a fresh thermostat & o-ring.

gruffalo

The o-ring was correctly installed, and the thermostat completely closes the passage to the upper radiator hose.

I found info on the temp vs. resistance characteristics of the temp. sensor i the WSM. Ill be checking that to verify that I am actually running cool. First I will boil it while measuring resistance, and then hook up my ohm meter while driving.

On my 81 CIS euro, it this sensor used for the temp gauge only, or for something alse as well?

MM

heinrich

If the therm closes all the way there is no way coolant can pass through the rad.

Kolbjorn S

It's too cold in Trondheim that's the problem ...

gruffalo

sure is