hi all - i've been battling with water in the trunk and the rear shelf ever since i got my 1985 S3 XJ6...i finally found it!...the rear shelf was rotted and the drain hoses were clogged adding to the rusting and leaking...so i took out the rear shelf and closed up all the holes with metal tap, windscreen sealer and underbody rubberized spray coating...see pics for what mine looked like...i also sealed every other hole imaginable on the rear shelf...including all the vents that sounded like cow bells...all sealed up...the rear windshield had leaked for years so i had that fixed but i still had water from the rear shelf and drain hoses...now i am sealed i hope it lasts...see pics

 

Good work !

Drains are important. Y'know, I don't think any or many cars are designed to be water tight. They largely depend on drains or drain paths to keep the water away from places where it doesn't belong.

I've fixed quite a few leaks that weren't leaks at all but clogged drains instead.

Cheers
DD