My '82 240 (W123) leaks into the trunk at every rain. I see it dripping from the under side of the parcel shelf. I understand that the backlight gaskets are prone to leaking, but I have sealed mine with no reduction in the flow of water--I expected at least a reduction.
I wonder if I am pursuing the wrong leak. Where do the vents in the rain gutter at the rear of the rear door openings drain. Is it possible that a drain hose ( if any) is missing? How do I access the area? What am I looking for?

ps. no sunroof, so I don't think thats the problem.