Ford Corsar Repair Manual page 388

CRANKCASE EMISSION CONTROL SYSTEM
Description
This system returns blow-by gas to both the intake manifold
and air cleaner.
The positive crankcase ventilation (P.C.V.) valve is provided to
conduct crankcase blow-by gas to the intake manifold.
During partial throttle operation of the engine, the intake
manifold sucks the blow-by gas through the P.C.V. 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 cleaner, through
the hose connecting the air cleaner 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 its 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 cleaner under all
conditions.
Inspection
P.C.V. (Positive Crankcase Ventilation)
With engine running at idle, remove ventilation hose from P.C.V.
valve; if valve is working properly, a hissing noise will be heard
as air passes through it and a strong vacuum should be felt
immediately when a finger is placed over valve inlet.
VENTILATION HOSE
1. Check hoses and hose connections for leaks.
2. Disconnect all hoses and clean with compressed air. If any
hose cannot be freed of obstructions, replace.