Crankcase Return Pipe - Early N52 - E90 325i/330i, E60 525i/530i, Z4 3.0si

This hose is part of the E90, E60, and Z4 crankcase vent system on the N52 engine. This hose is the return line from the oil separator to the oil pan (actually connects to a tube that runs into the oil pan), and includes foam insulation and a heating element.

Compared to the previous E46 system, the E90 CCV is much simpler but still prone to failure. The early E90 N52 crankcase vent system (CCV) has an external oil separator and hoses. The oil separator is bolted to the underside of the intake manifold with a hose coming from the valve cover, one going to the intake manifold, and a drain hose going to the oil pan tube. The oil separator and two of the hoses are insulated and heated to prevent sludge from building up inside the system. However, if the system is not working as intended too much oil in the intake air will lower the effective fuel octane, lead to drivability issues, and cause increased emissions. A completely blocked E90 CCV has the potential for very serious engine failure (hydrolock) if liquid oil ends up in the intake. Signs of a failing CCV include: whistling noises in the intake, blueish smoke in the exhaust, high oil consumption, and thick white or yellow gunk under the oil cap.

#4 in the diagram above.

BMW Fitments:

3 Series
E90 / E91 / E92 / E93 (06-13) > 325i
E90 / E91 / E92 / E93 (06-13) > 325xi
E90 / E91 / E92 / E93 (06-13) > 330i
E90 / E91 / E92 / E93 (06-13) > 330xi
5 Series
E60 / E61 (04-10) > 525i
E60 / E61 (04-10) > 525xi
Z Series
E85 / E86 Z4 (03-08) > Z4 3.0i N52