Crankcase Ventilation System: Operation
On gasoline models, during idle and low speed operation, high intake manifold vacuum pulls blow-by gases into combustion chambers for burning. During wide open throttle operation, low intake manifold vacuum and high blow-by gas pressure forces some crankcase gas through a hose to air cleaner.
On turbo diesel models, the oil separator valve regulates crankcase vacuum. The valve is normally open, allowing gases to flow out of crankcase and into turbo air inlet. When turbo inlet vacuum exceeds a pre-set value, oil separator valve closes, preventing oil from being drawn into turbo intake as well as preventing excessive crankcase vacuum.