BMW E90 oil separator: symptoms and replacement
325i330d
Can a clogged oil separator cause oil consumption and a lack of power?
Yes. Hardened carbon deposits can build up inside the separator and prevent its rubber diaphragm from working. Oil then gets into the intake manifold, which increases oil consumption and can disturb the operation of the intake manifold flaps.
Is replacing the oil separator difficult?
It depends on the engine. For example, in the 325i the separator is under the car and the undertray has to be removed out of the way. In the N57 diesel the replacement is quick: the quick-release fasteners are opened and the cover is lifted up.
Can the oil separator parts be bought separately?
BMW does not sell just the diaphragm or the cover separately; they belong to a larger assembly. Aftermarket parts (parts from other manufacturers) are available. There is no reliable information about the replacement interval.
Related articles
BMW E90 ABS sensor and wheel speed signal faultBMW E90 ABS unit replacement and fault codesBMW E90 adaptive xenon headlights not turningBMW E90 battery replacement: registration and codingBMW E90 automatic transmission adaptation resetBMW E90 automatic transmission jerks when coldBMW E90 front camber adjustmentBMW E90 Comfort Access key and antennas