oil retun hose

[Luke]

Is it a 4.4?

Are you talking about this part? Part 9?
RealOEM.com BMW E53 X5 4.4i Crankcase-Ventilation/oil separator

That was a pain, but it can be done. You will need to almost put your body into the engine bay leaning over. A small mirror helped me see down there. (like the dentist uses)

If that part is leaking it might be a leading indicator that your 2nd oil separator is failing too. (also called a cover here) Part 2. RealOEM.com BMW E53 X5 4.4i Intake manifold system
Pressure build up from the cover failing can cause that hose to fail. First weak point. Then you might have positive crank pressure that makes oil come out of the oil cap.

That can be much bigger a job if you need to replace it. But can be a DIY. I did it.