See Figures 1, 2 and 3
The crankcase emission control equipment consists of a positive crankcase ventilation (PCV) valve, a closed oil filler cap, a crankcase ventilation filter and the hoses that connect this equipment.
When the engine is running, a small portion of the gases which are formed in the combustion chamber leak by the piston rings and enter the crankcase. Since these gases are under pressure they tend to escape from the crankcase and enter into the atmosphere. If these gases are allowed to remain in the crankcase for any length of time, they would contaminate the engine oil and cause sludge to build up. If the gases are allowed to escape into the atmosphere, they would pollute the air, as they contain unburned hydrocarbons. The crankcase emission control equipment recycles these gases back into the engine combustion chamber, where they are burned.
Crankcase gases are recycled in the following manner. While the engine is running, clean filtered air is drawn into the crankcase through the intake air filter and then through a hose leading to the oil filler cap. As the air passes through the crankcase it picks up the combustion gases and carries them out of the crankcase, up through the PCV valve and into the air cleaner. After they enter the intake manifold they are drawn into the combustion chamber and are burned.
The most critical component of the system is the PCV valve. This vacuum-controlled valve regulates the amount of gases which are recycled into the combustion chamber. At low engine speeds the valve is partially closed, limiting the flow of gases into the intake manifold. As engine speed increases, the valve opens to admit greater quantities of the gases into the intake manifold. If the valve should become blocked or plugged, the gases will be prevented from escaping the crankcase by the normal route. Since these gases are under pressure, they will find their own way out of the crankcase. This alternate route is usually a weak oil seal or gasket in the engine. As the gas escapes past the gasket, it also creates an oil leak. Additionally, if the valve is improperly functioning and allowing excessive gas flow into the intake manifold at low engine speed, such as at idle, idle loping or rough engine idle will result. If idle loping or a rough engine idle is present, inspect the PCV system for proper operation prior to making any adjustments or repairs. Besides causing oil leaks and poor idle quality, an improperly operating PCV system allows these gases to remain in the crankcase for an extended period of time, promoting the formation of sludge in the engine.
- With the engine running, pull the PCV valve with hose attached, from the valve rocker cover rubber grommet.
- A hissing noise should be heard as air passes through the valve and a strong vacuum should be felt when you place a finger over the valve inlet if the valve is working properly. While you have your finger over the PCV valve inlet, check for vacuum leaks in the hose and at the connections. Replace any leaking hoses found in the system.
- With the engine off, remove the hose at the PCV valve. Shake the PCV valve. With the PCV valve removed from the engine, a metallic clicking noise should be heard when it is shaken. This indicates that the valve inside the PCV valve is free to operate. If no noise is heard, replace the PCV valve.
See Figures 4, 5, 6 and 7
- Disconnect the crankcase vent hose from the air cleaner.
- Remove the air cleaner and duct assembly from the engine.
- Inspect the PCV system vacuum hoses for cracks or deterioration and replace as required.
- To remove the PCV valve from the engine, pull upward on the PCV valve and hose to remove the PCV valve from the grommet in the rocker cover.
- Remove the PCV valve from the hose. Inspect the PCV valve as outlined above. If the PCV valve is in question, replace it.
- If the PCV valve hose was removed, connect it to the intake manifold.
- Connect the PCV valve to its hose.
- Install the PCV valve into the rubber grommet in the rocker cover.
- Install the air cleaner assembly and reconnect the crankcase vent hose, if removed.
- Start the engine and check for vacuum leaks.