The Positive Crankcase Ventilation (PCV) valve regulates the release of crankcase vapors during various engine operating conditions. As the engine operates, some combustion gas will escape from the cylinder by passing the piston rings. These gasses accumulate in the oil pan. Since a small amount of vapor is added on every piston stroke, the pressure within the oil pan quickly builds. If these vapors are not allowed to escape through a planned path they will quickly find their own exit, usually by forcing a hole in an engine gasket.
Since the gasses contain hydrocarbons and other pollutants, they cannot simply be vented to the atmosphere. The PCV valve allows the release of the vapors under controlled conditions back into the intake air stream. The vapors are then mixed with the incoming air, reintroduced to the combustion chamber and reburned. At high vacuum (idle speed and partial load range) the PCV will open slightly and at low vacuum (full throttle) it will open fully. This causes vapor to be removed from the crankcase by the engine vacuum and then sucked into the combustion chamber where it is dissipated.
REMOVAL & INSTALLATION
See Figures 1, 2, 3, 4 and 5
The PCV valve regulates crankcase ventilation during various engine operating conditions. Inspect the PCV valve system every 60,000 miles (96,000 km) or every 36 months. Toyota Motor Corporation recommends replacing the PCV valve every 15,000 miles (24,000 km).
- Open and support the hood.
- Locate the PCV valve in the valve cover or from the manifold-to-crankcase hose and remove it. Clean any gum deposits from the orifices by spraying the valve with carburetor or contact cleaner.
- Visually inspect all hose connections and hoses for cracks, clogs or deterioration and replace as necessary.
- Inspect the grommet the PCV valve sits in. Replace if necessary. If replacing, use a small amount of clean engine oil to help insert the grommet into the cover.
- Install the PCV valve. Make sure all hose connections are tight.