|
Well. That is the question, now isn't it? Air can leak past a piston ring, and into the crankcase from the intake manifold. if an intake valve is open and an exhaust valve is closed. If the exhaust valve is also open overlap will allow flow into the exhaust as well and prevent pressure from building in the piston cylinder. Also air can leak into coolant passages from the head. It can also leak from the cylinder, through a guide, into the valve cover area. Also from the compressor wheel seal to oil drain -> crankcase is always something. Borg Warner engineer warned me not to inject methanol pre-turbo because it will mix with drain oil.
So this is what you are trying to discover. The more sensitive you are to the pressure test the more leaks you will be able to find. because all rings leak, almost every seal leaks something sometimes. The PCV system is an essential oil control system which is supposed to "mop up" and put the entire system at a slight (or more) negative pressure (below atmospheric) to take care of all these leaking gasses. Keep them out of the engine oil and keep them from blowing out oil all over the place also, damaging seals and causing oil leaks.
|