see this post:

http://www.xoutpost.com/x5-e53-forum/...hlight=suckers

Dealer was probably correct, oil seperator froze up. What I've gathered from my research (540s and 740 have this same problem and its discussed in their respective internet forums) is that the oil seperator and vent lines on the 4.4 liter engine are pieces that just need to be replaced every 3-5 years, especially when you are doing short trips in cold weather, which does not allow the condensation build-up in the oil to burn off.

You need a new oil seperator. Its about US$50 or so for the part. Installation is a bit tricky for DIY, due to the limited clearance to reach back where it is located. I ended up taking my passenger side valve cover off (had to do vavle cover gasket anyways to fix oil leak), which made for better access. No special tools are required, its just hard to reach back there.

The heated pad is available from the dealer (like I said, really overpriced). I have not installed one, mine has worked fine with the new seperator and hoses. If I had to install a heater pad, I was going to use a 12 V heated handlebar grip pad from a snowmachine or fourwheeler, they are available for 20-30 bucks and should in theory work just fine. My idea was to use a relay triggered by ignition power and an underhood mounted toggle switch, so I could turn the heater on during the winter months and off during the summer. If you want to go this route, let me know, I'll provide more details and some pics of the parts needed.

But, so far mine has worked fine without anything.