How does the breather work to vent the gases in the valve cover to the air intake and yet not have the intake manifold pressurize the valve cover when the turbo is in boost? There is an electrically operated valve there, but my shop manuals don't describe what I see.
Usually there's a simple checkvalve.
There should be a small plastic check valve (one way valve) in the rubber hose from the valve cover to the manifold. This valve only allows flow from the valve cover to the manifold, not the other way. See
I thought that there was a one-way valve (not electrical) installed in the line from the cylinder head cover back to the intake manifold in turbo C900's specifically for that purpose?
I think it's what's called the PCV (Positive Crankcase Ventilation) valve.
Craig.
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