Why is oil mixing with water in reservoir only and not in engine

Asked by Feb 14, 2017 at 01:08 PM about the 2007 BMW 3 Series 328i Sedan RWD

Question type: Maintenance & Repair

4 Answers

37,945

Could still be a head gasket, they can leak oil into water passage without coolant going into oil. Time for a compression test, may want to run Block Tester as well.

1 people found this helpful.
120,175

Oil floats on water so it may be making its way to the reservoir which is at a high point.

1 people found this helpful.
87,145

If this is an automatic, it is possible the trany oil cooler inside the radiator has a leak.

3 people found this helpful.
95

Not familiar with the 320i but the 328 and stuff have a problem where the oil filter housing gasket leaks and mixes the oil into the cooling system.

2 people found this helpful.

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