Crankcase Vent Valve / Oil Separator, Genuine BMW - E46 M3, MZ3, Z4M

The E46 M3 oil separator is part of the E46 crankcase vent system and is responsible for extracting vapor from the oil so it can be returned to the intake and burned up in the engine. The liquid oil is then returned to the oil pan. A clogged or malfunctioning oil separator on the S54 will lead to excessive oil consumption (too much oil is getting burned), fault codes for fuel trim, misfires, and rough running. Now that these cars are getting older with more mileage, we're seeing more oil separator issues (it's notorious on the non-M E46 models).

Engines with more than 100,000 miles should have the oil separator and vent hose cleaned or replaced. The perfect time for this is during a routine valve adjustment. The oil separator can be cleaned by soaking it in detergent and letting it air dry. That may not clear all of the sediment and a complete replacement may be best.

This is the Genuine BMW E46 M3 oil separator. A new red seal is included (the black seal can be re-used).