Hi Bob:

I have done this job several times on the 3 240's that I have owned, and I have always had great luck with the GE Silicone that comes in the smaller tube that are available at Home Depot and Lowe's.

I recently replaced my original 1990 headlight with a used unit that was in mint condition. The original seal had just failed, so I separated the lense from the reflector, and then used my Dremel Tool with a wire brush attachment and removed the old tan sealer and re-glued the lense and reflector with the GE Silicone.

I secure the two pieces together with several large rubber bands overnight, and then install the resealed lense the next day.

Good luck with your project.
--
If it needs to be maintained, repaired or replaced on a 1990 240, I've probably done it. '90 240DL, 305,000 miles, will she make it to 400K ?? >>You haven't really worked on a car until you draw blood<< :-}