ike229

I have been having a problem for about 2 weeks now where I am constantly having to refill the expansion tank on my 924S after driving for awhile. The coolant is exiting through the overflow tube, which i found out by taping a bottle under the hood, and it fills up. I replaced my expansion tank cap with a "stant" 16lb cap from autzone thinking that my old cap was the problem.


Any ideas? Could the cap be the issue?

Steve PH

It could be the cap I cannot remember what the pressure rating is supposed to be. Also when I had a coolant leak (eventually traced to the rad itself) I found that after the engine got hot, the expansion tank would overflow.

I assume that was caused by the leak allowing the system to de-pressurise which lowered the boiling point of the coolant

Dilberto

Make sure the antifreeze mix is correct. It is essential- because it dramatically increases the boiling point of the coolant itself. Also, the cap affects cooling system pressure, without much margin for error. This means if the cap is bad, boil-over will occur. The system pressure needs to be tight-as-a-drum, in order to operate right.

Zach

Renn 951

head gasket...

Z-man

Are you overheating as well? If so, it could be the H2O Pump.

Another possibility is a stuck thermostat or blockage in the radiator.

-Z-man.

nickhance

Mine was the cap. I tried 2 different caps (both OEM), but it wasn't until I bought a brand new one that it stopped overflowing.

ike229

I replaced the thermostat thinking that could be the issue....

The car doesnt overheat... or run warmer than usual.