Crankcase Ventilation System

The pressure regulated crankcase breather system is installed on all recent vehicles. The system configuration varies model by model but functions the same. In the example below, the M62 engine has the crankcase ventilation valve mounted at the rear of the intake manifold. Vacuum supply ports are incorporated on the valve for the power brake booster and the fuel pressure regulator.

The pressure regulating vent valve varies the vacuum applied to the crankcase depending on engine load. The valve is balanced between spring pressure and the amount of manifold vacuum.

- At idle when the vacuum is high, the valve closes down and only allows a small amount of blow-by vapors to pass into the manifold.
- At part to full load conditions, the spring opens the valve and additional blow-by gasses flow into the manifold.

The crankcase ventilation system uses a cyclone separator to purge the blow-by gasses of oil vapors. The oil vapors condense in the separator and drain back into the sump.