Description
BMW has an issue with oil separators freezing in cold weather if the engine is not fully warmed up during driving. Common symptoms are a howling noise followed by oil leaks.
Crankcase breather valve used to purge the oil vapor from the engine block into the intake manifold. This valve has a single hose connected to it, running to the intake manifold
You should also look into replacing your valve cover gasket when changing the separator .