Maintenance Manual for J2 Sedan
Mechanical Part of Engine
132
II. Forced Ventilating System of Crankcase
1. System Illustration
The forced ventilating system of crankcase is used to bring the cylinder blow-by gas in crankcase back
to intake manifold.
It is the forced ventilating valve (PCV) which brings the cylinder blow-by gas in crankcase back to
intake manifold. With throttle partially opening, the intake manifold sucks blow-by gas of crankcase
through PCV valve. In normal conditions, the ventilation volume of PCV valve is sufficient to suck all
blow-by gas of crankcase and a little air. The vent air is brought into crankshaft through air intake pipe.
Ventilation hose inhales fresh air from the rear end of the air filter to the crankcase to keep the crankcase
pressure at a certain range. When the air throttle is fully open, the vacuum degree is not sufficient to
open PCV valve and thus unable to suck blow-by gas of crankcase. The air flows through connecting
hose in reversed direction. In vehicles with severe blow-by gas, PCV valve can not meet the
requirements because part of air may get into the air intake pipe at any time during operation.
