In Reply to: Fixing leaky Z3 3rd brake light posted by Etienne on March 02, 2001 at 09:58:38:
Once you have it apart you'll find it's a pair of plastic snap together pieces with a big rubber O ring on the outside. Very carefully clean the O ring and the surface around the outside of the brake light, it doesn't take much to cause a leak. A little piece of dirt caught in the paint would do it. That was my problem, I carefully picked it out. It's covered by the O ring so you don't see it.
Put it back together carefully seating the O ring on the outside. The key part is that when the 2 plastic pieces snap together you must hear a distinct click indicating they're properly seated. This was kind of hard to do, I finally got help to hold it on the outside while I pushed from the inside.
If you don't hear the click it's not right, the torx screws DO NOT clamp it together.
Good luck, be patient it's not hard just time consuming. Once you get it right you should be able to hit it with a garden hose full force with no leaks.
My Z3 (1998) got a paint job because some jealous idiot scratched it. It looks brand new again, but my 3rd brake light is a bit leaky now. The light unit is a bit loose from the trunk lid.
Does anybody know how the light unit should be fixed or sealed? Is it done a clamp/screwed with a rubber ring, is it glued or should it be sealed with a kind of rubber kit?