Wouldn't a warm trunk and cooler outside air cause condensation similar to what happens with a toilet tank? If so what is the source of the warmth in the trunk? I think it could be the fuel tank. The fuel is constantly being circulated thru the engine and warming up, thereby heating up the trunk. It would be interesting to compare your trunk with a similar vintage gas model to see if the same problem occurs because the gas isn't circulated up thru the engine.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

minor moisture equals condensation. significant moisture equals a leak. and if you have zero or close moisture elsewhere in the trunk, then the leak is in the trunk lid itself. the lower lip of the lid is capable of collecting moisture from the leak, and the humidity generated from that would collect on the lid.

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

To have massive condensation you have to have a lot of moisture present. It doesn't really matter how well ventilated the trunk is, when the car's stationary it's behaving essentially as a closed vessel. The volume of air in the trunk can only hold so much moisture, so if you're getting massive condensation there must be an external source of water.

MM

__________________
05 Passat TDI Wagon, 155k miles
05 Tacoma, 135k miles
96 F-250 7.3, 225k miles
85 MB 300TD, 275k miles
52 Dodge M37, 4BTA powered
52 Dodge PW, 23k miles
40 Ford Tudor Sedan (parts everywhere)

Be sure to remove the plastic liners on the fender wells when climbing in. This will show leaks coming from the side moulding trim, antenna mast and fuel filler neck.

I forgot to say, check all drains. The spare tire well has its drain hole, as do the fender wells right behind each rear wheel. All 3 should be clear of debris. Poke a screwdriver from the underside to clear the drains out.

Also, the bumper corners have mounting brackets to the fender (Euro versions) or the rubber ends have mounts going into the fender (Euro and US). Since the US have the large rubber covers, I wouldn't worry about them that much, but just the same, inspect for any signs of leakage. The US bumpers use two out of three holes for mounting the cover. The third (middle) hole has a rubber plug. Euro models use only the middle hole. Leaks here can get into the fender well. Coupled with clogged drains, they will pool water.

Uum, fix your door seals?

I spent dozens of hours chasing down an elusive `leak' in my 126 trunk with the only symptom being heavy condensation in the trunk lid. When you open it up sheets of water flow down the lid into the front corners and now (since I pulled the rubber plugs at the front corners to let it out) into the gutters. Floor and wheel wells are bone-dry.

All four of my doors have seals with splits on the top. When it rains, I see a small amount of water getting into the cabin through these splits. It does not look like much, but I am beginning to think it is enough be bring moisture into the cabin, which then raises the humidity, which then . . . gets into the trunk through the chassis openings behind the back seat.

Unfortunately, it is too cold and wet here now for me to fix the door seals without a big production. I'm going to have to pull the seals out for a few days, bring them inside, clean them up and sika-flex them back together.

If you beat me to it, let me know if this solves the problem.