: Cylinder pressure test for blown head gasket??

08-22-06, 11:02 AM
I need your help in understanding just what a cylinder pressure test is. I am looking at a 2001 SLS and want to have this test done along with other cooling system checks before I go too far. I am super sensitive because my 98 SLS is toast because of a blown head gasket. Ok to my question. Is the cylinder pressure test the one that tests the combustion pressure by using a tool that replaces the spark plug and you run the engine, record the value and then go on to the next cylinder until done then check the values against the factory spec? Or is it a test where the spark plug is replaced by a tool to which compressed air can be added to the cylinder and then checked for loss of pressure over a time period.

Also what should I expect to pay for this test and does it make sense for me to get the tool and do it myself?

Thanks for your help!!

08-22-06, 11:16 AM
You put air into each cylinder through the spark plug holes and look for air leakage into the cooling system. If you don't have the tools or experience it is best left to a good shop. About an hours labor.

08-22-06, 01:14 PM
You should also know that Cadillac revised the head bolts for the 2000-up Northstars to improve the head gasket reliability.

08-23-06, 01:04 AM

Your first description is a compression test. You do not run the engine but crank it with the starter motor.

The second is the cylinder pressure test and it is the more accurate (by far).