Volkswagen 2004 Jetta, Introduction Manual

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Engines
Crankcase Ventilation
A constant vacuum is maintained in the
crankcase through separate ventilation of
the crankcase and cylinder head. The
crankcase breather is connected to the
intake manifold.
The crankcase blow-by gases flow into the
cylinder head through the primary oil
separator in the oil filter module. Here the
blow-by gases mix with the gases from the
cylinder head and flow through a second
separator to provide additional oil
separation.
Since a turbo engine requires a more
sophisticated pressure control system, a
two-stage pressure control valve is located
on the cylinder head cover. If vacuum exist
in the intake manifold, blow-by gases flow
directly into the intake manifold.
If a boost pressure is present in the intake
manifold, a one-way valve in the pressure
control valve housing closes and the blow-
by gases flow into the cylinder head cover
ahead of the turbocharger. The system can
detect faulty installation of the pressure
control valve. Unmetered air is detected by
the reaction of the lambda probe.
Valve Cover
If a boost pressure is present upstream of turbocharger
If a vacuum is present in the intake manifold
Exhaust
Turbocharger
Gas Outlet
Intake
Manifold
Gas Outlet
Central
Crankcase
Gas Inlet
Oil Filter Module
Non-Return Valve
Non-Return Valve Pressure
Control Valve
332_057