leak down test

[shadow]

what's the proper way to perform a leak down test? i'm working on a 87 plymouth sundance turbo and think i got a blown head gasket and heard a leak down test can determine better whats wrong...can you help?

[Christopher]

First,you'll need a leak down tester,single or dual gauge,it doesn't matter,and a source of compessed air.For each cylinder,you will do the test the same way.Bring the piston up to TDC,with both valves closed,then hook up your adapter in the spark plug hole,open the valve on the tester and read the gauge,this will tell you the amount of cylinder leakage in %.A race engine at 5% is ok.A street engine that has more than 15-18% has something wrong with it.Now also as a diagnostic aid,listen for any air escaping....air out the exhaust is a bad exhaust valve,air in intake,intake valve,etc.