The positive crankcase (PCV) ventilation valve is a one-way valve in a car's pollution control equipment. It ensures that gases are continually evacuated from the engine. A defective PCV valve can cause an to run poorly or to leak oil.
The PCV valve circulates engine oil vapor containing gasoline fumes back into the engine to be burned, thus lowering emissions. The PCV valve also extends the life of the engine and oil. As the PCV valve constantly recirculates the air through the crankcase, it helps remove moisture that could cause sludge to form.he life of the engine and oil.
The PCV valve should be replaced every 30,000 to 50,000 miles (see your vehicle owners manual for specific service intervals). PCV valve failure may cause an engine to stall or run rough. A faulty PCV valve may cause high emission levels, which could result in a vehicle failing a state's smog test.
The PCV valve is normally located at the top of the engine. To replace it, the PCV hoses are removed, and the PCV valve is removed from the intake manifold (or valve cover). A new valve is installed and the hoses re-attached.