Have been informed by my workshop that my 996 4S is loosing coolant between two close visits (3 weeks in between)
Yesterday I drove a 300 km ride and before we took off I inspected the coolant level and it was ok.
Today I checked the level after the trip and the level in the reservoir had sank.
When I took of the cap to fill up it was pressurized and air came out of the reservoir.
After the air had went out the coolant level was up to a normal level and this without having to fill it up.
Is this really normal???

 

Normal.

 

If you are adding coolant, you should wait until the engine is cold. I would not unscrew the cap to check while the engine is warm. If your workshop says you are losing coolant, have they said where? Do you see coolant under the car? Have you ever had the expansion tank replaced, as those are known to age and crack.

 

No visible leaks but the car is apparently loosing coolant somewhere.

The system has been pressure checked by
my workshop and that showed no leaks.

I’m fearing a broken cylinder head gasket or a cracked cylinder but that’s not a common issue I’ve heard?

 

Take a look at this thread. Couple of good thoughts here: https://rennlist.com/forums/996-foru...g-coolant.html