Positive Crankcase Ventilation: Description and Operation

PCV Valve:

The Positive Crankcase Ventilation (PCV) system vents harmful blow-by fumes from the engine crankcase into the intake manifold for burning with the fuel and air mixture. The Positive Crankcase Ventilation Valve (PCV valve) varies the amount of blow-by gases fed to the intake manifold in direct relation to engine demand to prevent combustion backfiring into the crankcase. The benefits from the PCV system include the ability to:
- Maximize the oil cleanliness by venting moisture and corrosion from the crankcase
- Protect against crankcase explosions
- Automatically regulate the ventilation of crankcase blow-by gases to the intake manifold in direct relation to engine operating conditions

The amount of blow-by gas allowed into the intake manifold from the crankcase is controlled by the PCV valve. The PCV valve acts as a one-way valve; it does not allow anything from the intake manifold to pass into the crankcase.