Positive Crankcase Ventilation: Description and Operation

POSITIVE CRANKCASE SYSTEM DESCRIPTION

Fig. 87 POSITIVE CRANKCASE VENTILATION SYSTEM:

Between the crankcase and the intake manifold there is a hose which is connected to a nipple on the intake manifold. Between the valve cover and the air cleaner there is a hose connected for fresh air supply.
The partial vacuum that exists in the intake manifold during engine operation, creates a vacuum in the crankcase through the hose. Fresh air is supplied to the valve cover by the air cleaner and hose. A plate in the valve cover ensures that the fresh air circulates sufficiently in order to mix with the crankcase gases.
As fresh air passes through the air cleaner, impurities are prevented from entering the engine. During high or medium amounts of vacuum in the crankcase, which occurs during idling and when under light loads, the system operates as described above. When vacuum in the crankcase is less then that in the air cleaner, which occurs at full load and/or with large air-flow quantities, no fresh air is supplied. Instead, the flow in the connection between the valve cover and the air cleaner reverses and the crankcase gases pass both ways. In this way, the PCV system can deal with relatively large quantities of crankcase gases without any entering the atmosphere.

COMPONENTS:

Oil Trap And Flame Guard System:

Flame Trap (Guard)
-Prevents a possible backfire from entering the crankcase. Should the backfire enter the crankcase, it could ignite the blow-by gases. Periodic cleaning or replacement of the flame guard helps prevent crankcase over-pressure. Fig. 8.

Oil Trap And Flame Guard:

OIL TRAP
-Separates oil from gases and therefore reduces oil consumption and emissions. An additional benefit is, more effective control of the vacuum in the crankcase. Fig. 10.