Positive Crankcase Ventilation (PCV) System

GENERAL INFORMATION

Positive Crankcase Ventilation (PCV) System

1. PCV VALVE.

2. PCV HOSE.

The term "crankcase gases" refers to gases that pass through the gaps between the

cylinder walls and the pistons, as well as through the piston ring gaps. Both combustion products and compressed air-fuel mixture

break into the engine crankcase from the cylinders.

Crankcase gases contain a large amount of carbon monoxide and hydrocarbons. The PCV system is designed to prevent crankcase gases from being released into the atmosphere. The system operates

as follows. When the throttle valve is open and intake manifold vacuum is low, the PCV valve is fully open. This

is ensured by the valve spring. Crankcase gases flow freely through the PCV valve into the intake manifold, where they mix with fresh air and then enter the engine cylinders. When intake manifold vacuum is high, the PCV valve flow area decreases under the effect of vacuum. The flow of crankcase gases through the PCV valve into the intake manifold is reduced.

The PCV valve is primarily responsible for metering the flow of crankcase gases entering the intake manifold.

To maintain stable engine idle with the throttle closed, the PCV valve reduces the flow of crankcase gases into the intake manifold.

If normal engine operating conditions are disrupted and the volume of crankcase gases increases excessively,

some crankcase gases are routed through the ventilation hose to the air cleaner for further combustion in the engine cylinders.

Clogging or contamination of the valve or ventilation hose may cause the following:

– rough and unstable engine idle.

– engine stalling or low crankshaft speed.

at idle.

– engine oil leaks.

– engine oil contamination by oxidation products and sludge formation. A leak in the valve or ventilation hose may cause the

following:

– rough and unstable engine idle.

– engine stalling at idle.

– high crankshaft speed at idle.