See Figures 1 and 2
The carbureted gasoline 4-cylinder engines do not use a Positive Crankcase Ventilation (PCV) system valve. In place of the valve is a regulating orifice in the intake manifold. Blow-by gases are drawn through the regulating orifice into the intake manifold for reburning. During wide open throttle, the engine vacuum is not sufficient to draw enough vapor through the manifold, allowing part to be drawn into the air cleaner via the rear end of the rocker arm cover.
The fuel injected gasoline 4 and 6-cylinder engines use a PCV valve. The PCV valve meters the flow at a rate depending upon the manifold vacuum. If the manifold vacuum is high, the PCV restricts the flow to the intake manifold. If abnormal operating conditions occur, excessive amounts of internal exhaust gases flow back through the crankcase vent tube into the air filter to be burned by normal combustion.
The PCV system must be functioning correctly to provide complete scavenging of the crankcase vapors. Fresh air is supplied to the crankcase from the air intake, mixed with the internal exhaust gases, passed through the PCV valve or orifice and into the intake manifold.
If the engine is idling roughly, stalls at idle or has a low idle speed, exhibits oil leaks, oil is found in the air cleaner or sludge is found in the engine oil, a quick check of the PCV valve should be made. While the engine is idling, pull the PCV valve from the valve cover, place your thumb over the end of the PCV valve and suction against your thumb should be felt (indicating vacuum). If no vacuum exists, check for a plugged PCV valve, plugged manifold port, plugged hoses or deteriorated (leaking) hoses. Turn the engine OFF , remove the PCV valve and shake it. Listen for the rattle of the check needle inside the valve. If the check needle does not rattle, replace the valve with a new one.
The PCV system should be checked at every oil change and serviced with new parts every 30,000 miles (48,000 km).
Never operate an engine without a PCV valve or a ventilation system; doing so could damage the engine.Diesel Engines
See Figures 3, 4 and 5
The PCV system in a diesel engine works much the same way as in the gasoline engines. Combustion chamber blow-by gases are routed through the engine to the PCV valve. The PCV valve separates any oil vapor, which is returned to the oil pan, from the exhaust blow-by gases. The blow-by gases are then routed into the intake manifold, where they join with the stream of fresh air. The mixture of blow-by and fresh air enter the engine and are burned together. This system inhibits the blow-by gases from escaping into the atmosphere where they would contribute to global air pollution. For more information on the mechanics of combustion gases and pollution, please refer to Emission Controls .
To inspect the PCV system, check the diaphragm valve for damage and a sticky surface. Also check the oil separator element for wear. If any abnormal conditions are found, replace the PCV valve assembly. To inspect the oil check valve, remove it from the oil drain hose. Install a clean piece of hose to the inlet side of the check valve. Blow through the check valve-be careful, oil might splatter out of it. Air should pass freely through the valve in this direction. Install the hose onto the outlet nipple and once again blow through it. The check valve should not allow air to pass in this direction, Replace the check valve if it does not meet both of these conditions. Also inspect the PCV system hoses for damage or deterioration.
REMOVAL & INSTALLATION
See Figures 6 and 7
The PCV valve is mounted in the rocker arm cover for I4 engines, and usually in the left rocker arm cover for V6 engines. The PCV valve is connected to the intake manifold or throttle body by a vacuum hose.
- Using a pair of pliers, squeeze the tabs on the vacuum hose clamp together, then slide the clamp down the vacuum hose away from the PCV valve.
- Pull the vacuum hose off of the PCV valve outlet nipple.
- Pull the PCV valve out of the rocker arm cover grommet with a twisting motion. Take care not to damage the PCV valve mounting grommet.
- Shake the valve and listen for the rattle of the needle inside the valve. If the valve does not rattle, replace the valve with a new one.
- Push the PCV valve into the rubber grommet in the rocker arm cover.
- Slide the end of the vacuum hose over the PCV valve outlet nipple. Slide the hose clamp up over the nipple bulge to hold the hose in place.
See Figures 3 and 4TURBOCHARGED ENGINES
The PCV valve on turbocharged diesel engines is mounted on the rocker arm cover toward the rear of the engine.
- Disconnect the PCV hose from the PCV valve by either loosening the clamp screw, or by compressing the clamp tabs together. Slide the clamp down the hose, away from the valve. Pull the hose from the PCV valve.
- Remove the PCV valve-to-rocker arm cover mounting bolts, then lift the PCV valve off of the rocker arm cover.
- Disconnect the oil drain hose from the PCV valve in the same manner as the PCV hose, once access is gained.
- Remove the PCV valve from the engine compartment.
- Slide the oil drain hose onto the PCV valve and secure with the hose clamp.
- Position the PCV valve onto the rocker arm cover and install the mounting bolts. Tighten the bolts until snug.
- Connect the PCV hose to the PCV valve and position the hose clamp to secure the hose in place.
The PCV valve on non-turbocharged diesel engines is mounted above the rocker arm cover toward the rear of the engine.
- Disconnect the PCV pipe from the PCV valve by pulling it off of the PCV valve outlet nipple.
- Detach the oil drain hose and the breather pipe-to-PCV valve hose by either loosening the clamp screw, or by compressing the clamp tabs together. Slide the clamp down the hose, away from the valve. Pull the hoses from the PCV valve.
- Remove the PCV valve from the engine compartment.
- Slide the oil drain hose and the breather pipe hose onto the PCV valve and secure with the hose clamps.
- Connect the PCV pipe to the PCV valve.