water is getting into our 87 240 (high mileage, original owners)

I RTV sealed the broken sunroof, and there's no dripping around it, but a little water drips under the dash after a major rainstorm, and the inside of the car is soaked in condensation. when it gets wet, it gets unreliable (duh!), and is hard to start and stumbles til it dries out.

I note the windshield seal has 'shrunk' some at both bottom corners, and is caved in, and in the exposed channel is a bunch of green algae and such. I'm thinking resealing the windshield would be a good thing, but the car is nice enough that I don't want to do a funky job like slobber RTV on it.

 

The 75 leaked water. I had to reseal the firewall plates and some other areas behind the dash. It was rather annoying. Had to remove everything from the interior to fix those spots.
Luckily, the windshield didn't leak.

 

I would check around the windshield. The old style windshield seals (pre-'91) had a tendency to keep water around the lower corners of the windshield and rust through. Once they rust through you end up with leaks under the dash. This is hard to check without removing the windshield or tearing out most of the dash. Might be able to see up there by removing the instrument cluster.

 

I read about a 'fix' which is to remove the original seal, and the clips, and use black Polyurethane roofing goo all the way around.