Mike Diaz, I can’t say specifically about your engine. But on my ’99 Bonneville, non-supercharged, there are two O-rings in the picture here: The upper O-ring provides a seal for the MAP sensor, which lives in the same housing. The PCV valve, underneath the MAP sensor, also needs it’* own O-ring. (It goes around the body of the PCV valve, just below the flange).
Nerv, When the PCV valve O-ring is missing, serious amounts of vacuum leaks around the valve, making the “crankcase purge rate” WAY TOO HIGH –in fact it over-powers the PCV “fresh air return path.” At that point vacuum is present through the crankcase, and air then leaks into the engine at points of least resistance. –Most likely, around both crankshaft seals. (They are “directional/lip seals,” which offer high resistance to oil (and/or crankcase pressures) escaping from the engine, but offer very little resistance in the opposite direction.
Here is something not too pleasant to think about
: Along with the air going into the engine past the crank seals, goes whatever amount of black dirt, grit and grime that may have accumulated outside the seal. That thought makes me shudder.
Mike, in the interest of not “hogging up too much space” here, I can send a personal message to you, explaining the PCV system.
Once again, to everyone interested: YOU SHOULD NEVER HAVE VACUUM INSIDE THE CRANKCASE.
Engine manufacturers could just as well use a small air pump to purge the crankcase, but using intake manifold vacuum is much simpler, and actually is a basic design carried over from the 1940'*, when GM first used "positive crankcase ventilation" on engines in military trucks.
Thanks to all, Harry.