Anyone know if by doing a cooling system pressure test if this will tell you if your "O" ring seals are going bad.

 

Yes.


Sorry. Anyway, you will find your pressure dropping with bad O-rings. You must of course eliminate all other sources of leaking first.

another niftey test you can do with your pressure tester is to hook it up to the filler cap (NOT the AST!!!) and start the engine from cold. Look to see when the system starts to build pressure. If it starts building over 10 psi or so while still cold, you can suspect your O-rings. Ciriani's web site has a nice graph in the engine-mod/cooling-system section of the pressure versus temperature relationship for the car. what I found for my car was that it built 13 psi after about 1 minute of running, forcing coolant out the overflow. I had bad O-rings.

Good luck!