PCV SYSTEM
Article Text
1987 Volkswagen Quantum/Quantum Syncro
For Volkswagen Technical Site
Copyright © 1998 Mitchell Repair Information Company, LLC
Sunday, March 19, 2000 01:47AM
ARTICLE BEGINNING
1987 Crankcase Ventilation
VOLKSWAGEN
DESCRIPTION
Closed crankcase ventilation systems usually consist of one
or more of the following: PCV valve, oil separator, blow-by filter
and connecting hoses. For illustrations of typical PCV systems, see
Fig. 1.
OPERATION & SERVICE PROCEDURES
All closed crankcase systems draw crankcase blow-by, vapors
and gases into the combustion system rather than allowing it to
escape to the atmosphere. Crankcase gases mix with air/fuel mixture
and are burned in the combustion chamber. This is accomplished with
one or more of the following components:
PCV VALVE
Most crankcase ventilation systems use a PCV valve. It is
basically a one-way check valve, held closed by spring pressure when
engine is not running. This prevents hydrocarbon fumes from
collecting in intake manifold which can result in hard starting.
When engine is running, manifold vacuum pulls PCV valve
open allowing crankcase fumes to enter intake manifold. If engine
backfires through intake manifold, PCV valve closes and stops any
flow of gases. This prevents ignition of fumes in crankcase.
The PCV valve is usually located in a valve cover, intake
manifold or in-line. To check, idle engine and place finger over PCV
valve hose connection. If vacuum is not felt, PCV valve is defective.
Generally, if PCV valve operation is questionable, replacement is
recommended.
CAUTION: Do not suck air through PCV valve. Fuel vapor and petroleum
substances inside PCV valve are harmful.
OIL SEPARATOR
Some systems utilize an oil separator to separate engine oil
from crankcase vapor. Oil collected in the oil separator returns to
the oil pan by an oil return hose.
BLOW-BY FILTER
The PCV system usually contains one or more filters to
filter gases and/or fresh air before entering intake system. These
PCV SYSTEM
Article Text (p. 2)
1987 Volkswagen Quantum/Quantum Syncro
For Volkswagen Technical Site
Copyright © 1998 Mitchell Repair Information Company, LLC
Sunday, March 19, 2000 01:47AM
filters should be checked occasionally and replaced as necessary.
CONNECTING HOSES & PIPES
All crankcase ventilation systems use connecting hoses and
pipes to carry crankcase gases, engine vacuum and/or outside air.
Hoses and pipes should be checked for clogging and leaks and replaced
as necessary.
NOTE: Following figures are representative of typical crankcase
ventilation systems for various manufacturers.
Fig. 1: Volkswagen Crankcase Ventilation System
Courtesy of Volkswagen United States, Inc.
END OF ARTICLE
