Positive Crankcase Ventilation: Description and Operation

The crankcase is ventilated by a pressure controlled system. The oil vapors from the crankcase enter a labyrinth/oil trap which is integrated into the cylinder head cover (1). Here liquid oil is separated out, returned into the cylinder head and eventually the sump. The remaining vapors are drawn into the intake manifold (3) via a pressure control valve (2).
The pressure control valve is mounted on a heated flange plate located between the upper and lower intake manifold sections above the Differential Air Intake System (D.I.S.A.). It is connected to the rear of the cylinder head cover by a rubber hose, and varies the pressure in the crankcase continuously depending on engine load and speed conditions. This prevents blue exhaust smoke and excessive oil consumption on deceleration due to peaking manifold vacuum, and assures reliable crankcase venting during all other operating conditions.

Additional changes include:
- Oil dipstick approximately 1" (26mm) shorter compared to early M42 engines. Routing of dipstick and tube changed to accommodate location of the pressure control valve for the redesigned crankcase ventilation system.









PURPOSE
The Positive Crankcase Ventilation (PCV) system directs crankcase "blowby" to the intake system in order to prevent vapors from escaping to the atmosphere.

OPERATION
The crankcase is ventilated by a pressure controlled system. The oil vapors from the crankcase enter a labyrinth/oil trap which is integrated into the cylinder head cover (1). Here liquid oil is separated out, returned into the cylinder head and eventually the sump. The remaining vapors are drawn into the intake manifold (3) via a pressure control valve (2).