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Positive Crankcase Ventilation (PCV)

The combustion process produces many corrosive gases. The high pressure in the engine cylinder strokes force some of the gases to slip by the piston rings and into the crankcase.

To protect your crankcase oil from contamination the PCV system returns these corrosive gases back to the combustion chamber where they are burned alongside the regular fuel and air mixture.

The PCV valve extends the life of the engine and engine oil. The PCV valve requires very little maintenance. The valve and filter should be replaced 30,000 to 50,000 miles, according to your vehicle's manufacturer.

A smog check repair station can perform this repair along with an oil change for a minimal fee. You should consider replacing the PCV valve and filter every five to six oil change intervals.

Positive Crankcase Ventilation Valve

PCV Valve Location: The location of the PCV Valve is almost always around the top of the engine valve cover. It will consist of the PCV valve and pipe leading from the top of the engine valve cover to the intake manifold.

The system relies on the intake manifold's air pressure being less than crankcase air pressure. The lower pressure of the intake manifold pulls air from the breather through the valve, and into the intake manifold.

For the Smog Test: It is critical that the PCV system be clean, connected and un-plugged otherwise air flow to the intake manifold and subsequently the combustion chambers will be insufficient.

Which Type Should I Choose?


A plugged or malfunctioning PCV system will cause a smog check failure. PCV problems are primarily due to neglected maintenance and inadequate engine oil changes.

The hoses, filters and valve which this system consists of must be functioning and properly connected. It is pertinent that there be no cracks or leaks in with in the PCV system. Malfunctions of this sort will not only cause an emissions visual failure, but will increase tailpipe emissions as well.