[bobbycopeland870]

I am scratching my head on this PCV system. I understand the PCV valve is integral to the cam cover...got it. Now there is what appears to be a PCV hard tube that connects to the top of the intake and goes the inlet of the turbo air intake.

I orginally thought I read somewhere that it looks like it connects to the intake, but is actually connected to crankcase via channels on the head... If that's true I would expect positive pressure coming out of that male connection when I took off the Plastic PCV tube... Nope that thing was under major vacuum! If it's a vent to the crankcase shouldn't it be positive pressure and using vacuum produced by the air intake to "pull" the vapor out?

Then I move into the oil cap and again am wondering what the heck is going on. Call me crazy but the oil fill hole has both vacuum and positive pressure coming from it. If you take a tissue and put it over the opening it is definetly blowing, but then if you take the oil cap and put it on it, it sucks it down like it is a vacuum source... How is it both?

 

[jblackburn]

So a turbo car has vacuum coming from two places, depending on driving conditions:
-Intake manifold at idle, low throttle openings, and when coasting. Like a normal engine.
-Intake side of the turbo when the intake manifold is under positive pressure from the turbo forcing air into it.

There are a series of check valves in the system - in the intake manifold, that disc in the valve cover, and also in the tube that connects the top of the intake manifold to the turbo pipe. They serve to only let pressure go one way or the other.

The crankcase is always under negative pressure, but the Cruze routes the PCV system through a series of baffles the cam cover so it can dump oil vapor droplets back into the oil pan. So yes, the positive pressure you're saying is the air being sucked through the system and escaping the first point it can (oil cap). When the cap is put back in place, the vacuum leak is shut off and the PCV system circulates the air back through itself and into the intake.

Some oil vapor invariably ends up in the turbo and intake system, but it's an insignificant amount IMO. You lose almost no noticeable on these cars during a long oil change interval, and they have a tiny sump at that.

 

[bobbycopeland870]

The PCV tube should only allow air to blow one way right? If I blow from the intake side towards the turbo inlet no restriction. If I blow from the turbo inlet towards the intake, it is restricted, but I can still blow some air through it.