Positive Crankcase Ventilation: Description and Operation

Crankcase Ventilation System Description





An oil/air separator (1) is located on the left valve cover. Oil entrained gases from the crankcase enter the separator through a passage in the left valve cover. The gases flow through fixed and variable nozzles inside the separator which aid in removing oil from the gases. The gases exit through a hose (2) and are returned to the intake stream through a CDR (crankcase depression regulator) valve (3). The CDR valve limits crankcase vacuum to -1.5 kPa at higher engine speeds.

Oil removed from the crankcase gases at the separator pass through tubing (4) and down to a check valve (5) at the bottom of the engine front cover (6). The oil drain check valve prevents the back-flow of crankcase pressure upwards through the drain. It allows oil to flow back to the crankcase when drain column pressures are above 2 kPa.

Crankcase pressures are maintained between approximately -1.5 and +4 kPa during all engine operation modes.

With a closed crankcase ventilation system, it is normal for oil residue to be found on the turbocharger compressor wheel and inside the charge air cooler, pipes, and hoses.

No routine maintenance is required to the crankcase ventilation system.