What adhisive to use ?
 

Good day to all ...

I have '05 X3 3.0i with ~62k on the clock. It’s been a great car for me. New tires, (a new clutch thanks to the previous owner but covered under warranty), and routine fluids are all that stood in the way of a simply perfect vehicle for me.

Well, that's not necessarily true, I had the dreaded 'window regulator' (passenger side rear door) go on me about 3 weeks ago. I took the door apart, and the 'dog bone' was indeed the issue. The quickie fix with attaching a piece of metal to keep the guide in place did not work, so it was a complete replacement for me. Dealer wanted $181 for the part, but I opted for aftermarket and $109. New part is in place, and the window is working. Now, for my question...

What adhesive did you use to put the vapor barrier back on the door? I can't reuse what is already there as it's lost its stickiness / tackiness. I called the local dealer, and the parts guys referred me to the service guys, and the service guys can't/won't tell me, but referred me to the BMW web site where all the tidbits can be found ... for a price.

Is this simple as applying RTV, or silicone?

i would use a adhesive caulking sold in any hardware store not sure the plastic will adhere to the silicone for very long. you could also use a double sided tape which might actually be the best get a good quality brand like 3M and narrow like 1/4 in wide should be able to make most of the bends with no breaks.
disclaimer no experience with this just what i would do.

Did you try to use the hairdryer to soften the existing adhesive and re-use it?