Sealant on 1987 325E rear window replacement?
Job finished with vaseline help,
This process worked for me. I took my time and was careful not to overstress the window or rubber seal.
1.) Apply vaseline inside the rubber window seat groove. This will help if you have to slide the window in position to start.
2.) Seat the window as much as you can. Tape a thin plastic strap to the end of a flat head screwdriver. Use this to push the rubber seal from the car inside around the window. Push until the seal edge overlapps the outside window edge.
Note: Take your time and only do a half inch area at a time.