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Originally Posted by Ranger  I don't see how that is going to tell you anything about valve stem seals. That is more for testing compression, rings & valve seats. You could also use the separate hose for a cylinder pressure test to check for bad head gaskets. |
Larry, a leak-down tester puts air in the cylinder at a lower psi then direct shop air (120 psi or more). You can hold your finger over the fitting. It measures the percentage of air leaking past the rings & or valves. If the leakage is 20% or less and you have an oil consumption problem, you know it's the guides/seals. If it's high, 40% or higher, the rings are suspect. You'll also hear the air coming from the crankcase.