One of the areas of water egress into trunk is a torn weather seal. Once torn it loses it's compression strength and allows water entry past the seal. Unfortunately it's very expensive to replace. I believe around $250+. Here is a low cost quick fix that has lasted me more than 7 months. It involves inserting foam weather strip into the torn seal to increase it's compressibility. Here is a video...
I have a 2010 35i and noticed the seal at the top of the boot lid nearest the head rests has perished in two places. I believe the part number is 51767191265 on www.realoem.com
I have to say I fell off my chair at the price BMW wanted. Approx £450 special order from Germany and non returnable. Looking on alternative web sites it’s nearly as bad.
Has anyone else has this seal fail and where did you source a replacement?
Just some pics of the issue.
So need to confirm item No 4 on the schematic diagram is the right part if I have or order?
Yes, that video is mine and the fix continues to work well. However, my seal is now degrading in several additional areas and I've obtained an used seal in excellent condition. Would like to install before winter. Was wondering if anyone has done this, so I can estimate how much time I need to complete. Also, how much disassembly is required to install?
Turns out it was an easy repair. Didn't have to remove any interior parts. Note, there is a torx screw fastening the seal on both ends. If you use a right angle drive, you can remove the screws without removing any trim. Just pull trim back. Picture of tool is attached.
Lessons learned. Attach seal at both ends first to install torx screw. Then work your way around to finish. I used 3M gasket sealant.