If cabrio then this could apply:
 | SI B51 29 08
Body Equipment | November 2008
Technical Service |
SUBJECT
Water Leak into the Trunk Area
MODEL
E64 (6 Series Convertible) produced from 8/2006 to 5/2008
SITUATION
The convertible top stowage compartment has 4 drains to allow water to exit from it. Over time, these drains may become blocked by leaves and debris. Once these drains are clogged, water may collect and overflow into the trunk and may damage various electronic components.
Cars produced up to 8/2006 should be addressed per the Service Action noted in
SI B51 26 08.
CAUSE
Clogged stowage compartment drains
CORRECTION
Unclog and then modify the affected drain. In isolated cases, new drain(s) should be installed. Replace any damaged electrical components.
PROCEDURE