Positive Crankcase Ventilation: Description and Operation

PURPOSE
The Positive Crankcase Ventilation (PCV) System prevents blow-by gasses in the crankcase from escaping into the atmosphere.

OPERATION
This system returns blow-by gas to both the intake manifold and air inlet tubes.
The PCV Valve is provided to conduct crankcase blow-by gas into the intake manifold. During partial throttle operation, the intake manifold sucks the blow-by gas through the PCV Valve.
Normally, the capacity of the valve is sufficient to handle any blow-by and a small amount of ventilating air.
The ventilating air is then drawn from the air inlet tubes, through the hose connecting air inlet tubes to rocker cover, into the crankcase
Under full-throttle condition, the manifold vacuum is insufficient to draw the blow-by flow through the valve, and it's flow goes through the hose connection in the reverse direction.
On vehicles with an excessively high blow-by, some of the flow will go through the hose connection to the air inlet tubes under all conditions.