Mercedes crankcase ventilation malfunction

This fault is a super common one on the new 4cyl no matter what chassis it is in. 

It’s a decent job, a lot of work the first time around because you must replace the PCV oil separator as it does not come separate.

I believe the problem lies in the oil separator most of the time, freezing due to moisture; or blocking due to oil sludge. There is just a flimsy spring-loaded check valve in the oil separator.

Here are the locations of all the components