Positive Crankcase Ventilation: Description and Operation

General Description
A crankcase ventilation system is used to provide scavenging of the crankcase vapors. Blow-by gases are passed through a crankcase ventilation oil/air separator into the air cleaner outlet resonator. The oil/air separator is inside the valve rocker arm cover and allows any scavenged oil to be returned to the crankcase.

Operation
The only flow through the oil/air separator is the combustion blow-by, as there is no fresh air inlet to the crankcase. The primary flow of blow-by into the separator is through the openings inside the valve rocker arm cover. The oil/air separator causes oil, which may be suspended in the blow-by gases, to be separated and drain back to the crankcase. The blow-by gases are then drawn into the air cleaner outlet resonator by normal engine vacuum and burned in the combustion process.