Ok, on Tuesday I decided to dive into this sagging headliner repair because the moron at the auto upholstery shop (the same shop that installed a new powered soft top on my 2000 Z3) told me that he would t touch this job because of all the sensors in these "newer" cars.
Anyway, the repair was actually really easy. There are four T-15 torx screws along the leading edge of the soft top that hold the plastic trim piece up. These are easily accessible if you open the top about half way. There is another torx screw in the center of this piece near the rear edge underneath the rectangular access port which just pops off. Finally there are two Phillips head screws, one on either side of the plastic trip piece near the trailing edge of the plastic. They are harder to reach as they are u dear the cloth top on the side. The top has to be in just the right position or the screws will be blocked by the frame on the side. Once these seven screws are out you can pop the plastic trim piece off. The leading edge of the headliner is attached to this piece so you can just drape it over the seats.
This exposes the problem with the sagging headliner. There is a seam in the headliner which goes from left to right and sewn into this seam is a piece of black plastic angle. There are about 12 holes in this plastic and screws are used to fasten this plastic to the main aluminum arch of the frame. Over time the holes in the plastic break through the edge of the plastic and the headliner falls and sags.
On the main aluminum arch there is a thin slot along the leading edge where the screws are threaded into which support the headliner. This is great because that means all you need to do is to drill new holes in the plastic piece and turn the screws into a new location along the main arch. Just make the holes in the plastic support slightly smaller than the screws so that the screw bites into the plastic. That acts as a second pair of hands to hold the screw while you are trying to fasten the screw into the aluminum arch. It helps to have another person to hold the leading edge of the soft top up to take tension off the headliner but you could just tie it up to something too.
Sorry for not having pictures up this really wasn't a planned repair. I just dove into it without thinking about documenting the process. At any rate this was a very easy repair and anyone with basic tools could do it. The only "special" tool I would recommend is a small 1/4" drive ratchet with a T-15 Torx bit for getting into the tight spaces when reattaching the headliner to the main arch. You just won't be able to fit a torx screwdriver in that space for most of the screws. I hope this is helpful.
Ken
