GM Service Manual Online
For 1990-2009 cars only

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 mounted to the engine block 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 a hose from the timing chain housing. 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.