I had the same problem with my 2004 3.0 last year, both rear brake lines rusted through from the outside causing brake failure. My wife was driving at the time of failure and she was lucky to be local and made it home safe. She knew something felt different but didn't realize how serious this was! When I checked it out in my driveway, fluid poured out onto the ground when I pressed the brake pedal.

Changing both rear lines at the dealer cost me over $1000.

Someone mentioned on here that they were able to get BMW to pay for the labor portion of the bill which was probably 90% of the bill. Has anyone else been successful getting BMW to help out???????

I've never had an issue like this on any of my previous vehicles.....and I hold onto cars for ten years.