Porsche Enthusiasts Club Forum

Ok, just need a quick sanity check.
Finally got the 944 turbo running again after spending the last 2 and a half years restoring and modifying.
I have completely rebuilt the engine with all new bearings, seals, Garrett turbo, Vitesse maf etc. etc. etc.
Started up in the garage and runs well then let it cool down and about 100 mills of coolant has gone, this can be repeated and after about 20 minutes running 100 mills of coolant goes each time.
I have fitted a mls head gasket and after reading a number of horror stories decided that this must be the problem so last Saturday I swapped this out for another brand new mls and used the copper head gasket spray between each layer, rebuilt engine and just the same.
Some facts
There are no visible coolant leaks anywhere, including inside the car. (All hoses and pump are new)
The car does not overheat and the fans are working fine
No steam from exhaust (although weather is warm)
Steam vent fitted to head so it is bleeding correctly
No signs of coolant in the oil
No signs of oil in the coolant
Only very slight moisture in the oil filler cap after cooldown
Plugs look normal
The head was skimmed for a mls
The block is flat
Well that’s about it, am I missing something ? any ideas ?
Unless someone can come up with something then the heads coming off on Wednesday, going for pressure test and an oem head gasket is going on.

Thanks in advance.

Either over filled or defective (weak) coolant pressure cap.

Could also be the oil filter manifold o-rings. What might be happening is that with the coolant filled to the maximum, once the engine gets hot, the pressure with that volume of coolant pushes 100ml past the o-rings, which then ends up steaming off in the oil, once this volume has been removed from the coolant, the pressure is just that little bit lower to allow the seals to seal once more.

Just a hunch.

Just a thought!
In line with what Jon has said :- does it loose 100ml every time it is started and cooled down, whatever the level ? eg even if its near the low mark to start with.
The reason I say this I had a similar problem on a Land rover TD5 if it was filled up it lost coolant (every time), if it was nearer the low mark it didn't.
Clive

Thanks for the replies, very much appreciated.
I have only ever filled the expansion tank to just above Min and the filler cap is new, also checked for leaking and is fine.
Jon, the oil manifold o rings are new as well as the gasket, also it is the later type. As the oil pressure is considerably higher than the coolant wouldn’t oil be in the coolant rather than the other way around ?
Definitely no oil in the coolant.