Now I know measuring negative pressure of a crankcase can help one determine the condition of the piston rings. With that in mind, I have 2 questions:
1) the negative pressure in the crankcase is achieved when the piston is on its compression or exhaust stroke?
2) monitoring negative pressure in the crankcase is a pretty good way to avoid the labor time to complete a "leak down test"?
As always, thoughts appreciated and thanks in advance.
Negative pressure is achieved by the pcv valve and manifold vacuum.
The monitoring of negative pressure in crank case does not eliminate the need to do a leakdown test as it is 1/4 of the places leaks can go. I.E. crankcase, exhaust system, intake and out the coolant system are the 4 possibilities. The leak down test will eliminate 3 out of 4 possibilities leaving coolant system which can be tested via a pulse sensor, chem test (to an extent), pressure test of coolant system, rubber glove on coolant cap, evaluation of the oil in oil pan and coolant leaks around cylinder heads.
