This past May, I did some major sunroof repair on my '90 760 GLT. I replaced the slide mechanism using another from a pnp. I replaced the "seal" surrounding the roof. This replacement came from Tasca Volvo for $44.00. The roof will have to be separated from the slide mechanism in order to make the replacement happen.
- When working an order from Tasca, ask them first to fax a schematic. This will come as an exploded view. They will accompany the schematic with a list of parts including part numbers. This makes it easier to communicate over the phone and ensures each party is speaking the same terminology.
- Make certain your sunroof drain lines are clear. I used a plastic coated wire cable to roto-router the drain lines.
- There is a straight length of black rubber that fits on the slide mechanism aft of the roof. It runs port to starboard. Make sure it is fitted properly.
- I don't recall a "square piece of white foam" serving any significant purpose relating to leak prevention. I have a faint recollection of having sighted one and thinking it might only serve as a cushion.
- Inspect the "seal" that surrounds the circumference of the sunroof. I replaced mine because of a gap between the ends could not be kept closed. Further, the seal has a stiff fiber bristle feel. Compared to the new replacement, the older one had seemed to be worn. Also, I couldn't maintain a uniform seal fit around the sunroof, another reason for the replacement.

Mike
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'83 245 GLT, '90 760 GLT