Positive Crankcase Ventilation
The purpose of the PCV System is two-fold. It regulates crankcase pressure and ventilation of fumes from the crankcase into the intake manifold. It also works as a check valve to prevent any intake fumes from entering into the engine.
The PCV system consists of the PCV (Positive Crankcase Ventilation) valve, grommet, tube, and an air supply hose to allow air to flow into the crankcase. Check around these fittings for any signs of oil. Everything must be tight. Oil leakage indicates a problem with the system.
It's a simple system where a light spring holds the valve in the open position when the engine is off or when there is a drop in manifold vacuum. This results in maximum crankcase ventilation. When the engine is at idle the higher manifold vacuum pulls the valve upward blocking the port to the intake manifold. Spring pressure verses vacuum pressure.
A stuck closed PCV valve will cause excessive crankcase pressure resulting in leaks past oil seals and gaskets. A stuck open valve or leaking PCV hose will cause driveability issues like surging. Some air supply hoses have an air filter or filament to clean the air entering the crankcase. Check this for oil or anything clogging it and replace if necessary. A closed or tarnished PCV valve will cause oil to back up into the breather. A PCV valve should rattle when shaken. If the valve doesn't rattle then it must be replaced.
The PCV system was implemented in 1963. It is used to recycle fumes from the crankcase back into the intake manifold for combustion instead of just releasing them into the atmosphere.
