General information
Scheme of crankcase gas flow in engines equipped with a typical PCV system
PCV system (refer to illustration above) serves to reduce the emission of hydrocarbon compounds into the atmosphere due to the removal of crankcase gases from the engine. The unit is purged by forcing fresh air coming from the air cleaner through the crankcase, where it mixes with accumulated fumes and gases escaping from the combustion chambers and is discharged through the PCV valve into the intake manifold.
The main components of the system include a PCV valve, an air intake and a set of vacuum hoses connecting these devices to the engine.
In order to maintain stable idle speed, the PCV valve shuts off the purge flow when the vacuum in the intake manifold is deep. In the event of a malfunction of the engine (such as worn piston rings) the system removes excess crankcase gases through the ventilation tube back to the air cleaner and burns them in the combustion chambers.
The intake of crankcase gases into the engine is carried out through the throttle body, which eventually begins to become covered with tar deposits, especially in the area of the throttle valve. In view of the foregoing, the throttle body should be cleaned from time to time.
Examination
1. To check the proper functioning of the PCV valve, it should be released from the rubber seat sleeve and shaken. A serviceable valve, when shaken, should make a noise coming from the locking needle - if necessary, replace the valve assembly.
2. Start the engine at idle and press your finger against the hole in the valve - there should be a vacuum inside the assembly. If vacuum is not felt, first check the patency of the vacuum hose, then (if the hose is ok) replace valve.
Replacement
1. Pull vertically upwards to remove the valve from the rubber seat. Assess the condition of the bushing, replace if necessary.
2. If the valve is clogged with tarry deposits, it is also possible that the connecting hose will be blocked, - remove the hose and flush it with a solvent.
3. After flushing the hose, check it for signs of material aging and mechanical damage. Track reliability of fixing of a hose on receiving unions.
4. If necessary, replace the PCV valve.