This pipe connects to the front of the intake manifold and runs back to Y connecter at the back of the intake manifold. An unfortunate and ongoing issue with modern BMWs is with the oil separator, or crankcase ventilation system. Over time, the oil vapours that the system is designed to capture and recirculate can cause clogged lines and other blockages, resulting in oil leaks or reduced engine performance. These plastic pipes are also notorious for cracking. We offer this replacement hose from Febi Bilstein. 

OEM Part Number: 11617504536
Rein Part Number: ABV0109R