Originally Posted by
shivers
Make sure the engine is warmed up before you do the test, otherwise your numbers will be skewed. A compression check will assess the health of the bottom end (i.e., rings). You'll need to do a leakdown test to test the upper half of the engine.
no, a compression check will let him see if anything is blown. the things it doesnt help with are things like oil rings, which are outside the scope of the combustion chamber.
if compression is off you then need to do a leakdown test to see where the bubbles form (if it's in the radiator fluid you have a blown headgasket into a coolant line... etc)