System Overview; Crankcase Ventilation System - Volkswagen Golf Diesel 2009 Mode D'emploi

System Overview

A primary oil separator is installed on the cylinder
block just below the engine coolant pump. A baffl e
plate in the oil pan upper section prevents engine
oil from being drawn out of the sump at the gas
extraction point. In the primary oil separator, the
blow-by gases fl ow through a labyrinth to separate
coarse particles from the oil. The primary oil
separator has two separation stages which work on
the baffl e-plate principle.
The separated oil fl ows back along oil return lines
into the oil pan. The blow-by gases continue to fl ow
from the primary oil separator through a channel
in the cylinder block to the cylinder head. The large
cross-section channels results in a low crankcase
breather gas fl ow rate which prevents oil droplets
from travelling along the sides.
A fi ne oil separator is integrated with the cylinder
head cover. A single-stage cyclone separator with a
parallel bypass valve fi lters out any residual ultra-fi ne
oil particles.
Fine Oil Separator
Primary Oil Separator

Crankcase Ventilation System

The separated oil fl ows into the cylinder head
through a port in the cylinder head cover; from there,
the oil is returned to the oil pan. To prevent intake
of the engine oil under excessively high vacuum, a
check valve is installed at the end of the oil return
duct. This check valve is installed in the honeycomb
insert in the oil pan.
The blow-by gases fl ow along a duct integrated in
the cylinder head cover to a two-stage pressure
regulating valve. The pressure regulating valve
prevents excessively high vacuum from developing
within the cylinder block.
The pressure regulating valve is installed in a housing
together with two check valves. The check valves
regulate blow-by gas fl ow depending on pressure
conditions in the intake manifold. If a vacuum is
present in the intake manifold (for example, at low
engine speed) when the exhaust gas turbocharger
is not producing boost pressure, the blow-by gases
are drawn directly into the intake manifold. If boost
pressure is present, the blow-by gas is inducted on
the intake side of the turbocharger.
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