Crankcase Venting

The M42/E36 engine is equipped with an integrated primary/secondary crankcase vent system, in order to keep the level of moisture condensate in the intake air passing through the throttle body as low as possible. This avoids contamination of the idle speed control valve and the throttle body.

The primary crankcase vent operates through a large-bore flexible hose which discharges into the air intake system ahead of the throttle body plate (butterfly).

The secondary crankcase vent discharges into the air intake system by way of a channel integrated into the throttle stub pipe housing. In this channel there is a 1.8 mm diameter nozzle to control the flow volume.


Two heating elements on the throttle body, through which the coolant flows, ensure that the crankcase vent system is intensively heated.

The secondary crankcase vent continues to function until well into the part-load operating range. The primary crankcase vent only takes over when the full-load operating range is reached, the changeover being governed by the difference in pressure between the crankcase and the air intake system.