Crankcase Ventilation System; Description - GMC G Service Manual

6E2-4 DIESEL EMISSIONS
0
Figure 5 — Heavy-Duty Emission Control System — LL4 (G-Models)

CRANKCASE VENTILATION SYSTEM

DESCRIPTION

PURPOSE
The crankcase ventilation system (Figures 6 and 7) is
used on all 6.2L (LH6 and LL4) diesel engines and is
designed to produce a negative crankcase pressure. This
lower pressure reduces engine oil leaks. The system uses
a crankcase depression regulator valve. Refer to Figures 2
through 5 for location of the valve on the vehicle.
The crankcase depression regulator (CDR) valve is
used to regulate (meter) the flow of crankcase gases back
into the engine. The valve is designed to limit vacuum in the
crankcase as the gases are drawn from the right valve
cover, through the valve, and into the intake manifold (air
crossover).
The intake manifold vacuum acts against a spring
loaded diaphragm to control the flow of crankcase gases
(Figures 7 and 8). Higher intake vacuum levels pull the
diaphragm closed to the top of the outlet tube. This reduces
the amount of gases being drawn from the crankcase. As
the intake vacuum decreases, the spring pushes the dia­
phragm away from the top of the outlet tube allowing more
gases to flow to the intake manifold.
Refer to MAINTENANCE AND LUBRICATION (SEC.
OB) for diesel crankcase ventilation system maintenance
requirements.
\T \ CRANKCASE DEPRESSION REGULATOR VALVE
GO INJECTION PUMP
[7 ] FAST IDLE SOLENOID
[ ] OIL FILL PIPE
4
EH
FRONT
OF
VEHICLE
NOTICE: Do not allow any solvent to come In
contact with the diaphragm of the Crankcase
Depression Regulator Valve, because the dia­
phragm may be damaged.
Figure 6 — Crankcase Ventilation
5S 1406-6EA