McDonaldD - Amazing write-up! Very happy to find someone with the exact problem and it appears that you fixed the issue! Congrats and thank you for taking the time to share your experience with us. Very encouraging that it could something other than a blown head gasket that will cost us thousands to fix! I was recently laid off and can't afford a $8K fix, so your post is a relief and gives me hope. I love my X5 and but for the "cloud of shame" the car runs like a champ!

My white smoke issue started about a month ago - my 2006 X5 4.4L (E53/N62) with 80,000 miles - "an embarrassing cloud of shame - typically after accelerating from prolonged idling." Happens more noticeably on warm sunny days. Only difference is the smoke is only coming out of the driver's side tailpipe.

I replaced my Pressure Regulating Valves, as many suggested, but that didn't help since they weren't torn.

McDonaldD - I am a DIYer that is somewhat mechanically inclined and recently completed simple stuff like changing my brake pads and rotors, oil/filter changes, etc. But what you are describing seems a little over my head. So I would like to ask for a favor and propose to ask for your help. It appears that we live close by, I am in San Francisco. I propose that I will buy all the parts and over a day or two get your help with doing exactly what you did on your X5 and I could compensate you for your time. It would be a great learning experience for me as well. That would be a tremendous help to me, let me know if you are willing and have the time.

BenSF