I noticed the other day that a component (breather valve) was not fitted properly (the clip that held the valve cover breather in place was sitting between the O-ring and the lip, instead of fastening the component to the top of the engine) and since have been trying to learn more about the PCV system in my car.
When I removed the valve I saw that there was a fair amount of oil in the pipe running from the air intake.
I believe this is a no-return valve, and my first thought is that it is meant to allow the clean air to flow into the intake manifold along with the blow-by when the pressure above the valves/in the crankcase is low enough, but prevent blow-by from entering the air intake when it is high.
Alternatively, there is the (very high) possibility I've misunderstood the PCV system in this car and in fact that valve is the channel through which the blow-by enters the intake manifold in which case it would be expected that it was filled with oil.
- Have I understood the PCV system correctly?
- Should there be oil in my air intake?
The car is a 2002 Audi A4 2.0l (B6 body, no FSI).