Volkswagen Golf Diesel 2009 Mode D'emploi page 275

Crankcase Ventilation System
Positive Crankcase Ventilation
This system supplies the crankcase with fresh air to
mix with blow-by gases. Fuel and water vapors in the
blow-by gases are absorbed by the fresh air and then
discharged through the crankcase ventilation system.
Fresh air is drawn in from the intake air system
downstream of the air fi lter and Mass Air Flow
Sensor. A breather pipe is connected to the cylinder
head cover via a check valve (PCV valve).
Opening Pressure
26
Cutaway View of Crankcase Breather Valve
A
Housing
Sealing Disc
Retainer
B
Direction of Flow A-B
Pressure Greater Than
- 0.10 psi (-7 hPa)
The PCV valve ensures a continuous air supply and
that unfi ltered blow-by gases cannot be aspirated
directly.
The PCV valve is also designed to open under high
pressure inside the crankcase. This precaution
prevents damage to seals due to over-pressure.
PCV Valve
Cover
Compression Spring
Silicone Valve
Disc, Perforated
O Ring
Direction of Flow B-A
1.4 ± 0.21 psi
(100 ± 15 hPa)
O Ring