Hi guys, my 240D is forced to sit outside in the Pacific NW. As we are into Fall and soon Winter, I've noticed that the changes in temp and the moisture in the air causes massive amounts of condensation to form on the inner trunk surface. The floor of the trunk is dry (I've fixed all the leaks from trunk seal and rear window), but the inner surface of the trunk lid has massive amounts of condensation, likely from the combination of moist air and big swings in temperature throughout the day.

What do you guys do to combat or avoid this?

Thanks,

Packman

__________________
83 240D - 4 speed manual - Manilla Beige
189K miles, Tachometer mod, cool wooden shift knob from PeachParts, CocoMats, Original factory paint, manual windows, manual sunroof. Starting to add AudioWrap to this car too!

I'm in the same boat as you. I'm curious to see what others have to say.

__________________

Ventilation would help. Does your car have vents down low in the trunk? ( the area where the quarter panel meets the well. ) I'd be real tempted to use some small computer muffin fans to keep air moving. To get real tricky, use a humidastat / timer and -or solar panel.

Are you sure you don't have a leak. My antenna grommet was leaking on my car when I bought it. There were a few rust throughs on both sides where the area behind the wheel well meets the back panel.

I didn't notice much until I took out the plastic panels that fit into the wheel wells.

__________________
85 Merc 300D - Unwinding 31 years of wear
86 VW TD
Mahindra Diesel
Iseki Diesel

In 2007 I didn't own a diesel.

I'm also wondering if you don't have a leak somewhere. I don't have any significant condensation in either of my 240D's, although I definitely have a leaky trunk seal in the '83. A "massive amount" seems only attainable if moisture is getting in somehow.

In addition to the antenna seal, I'd be real suspicious of a leaking tail light. Those can be tricky to find.

__________________
'79 240D

Hi guys,

Thanks for all the helpful suggestions. I've checked the rear windshield seal (OK), the trunk seal (OK), and just pulled out the carpeting, metal panel in front of the gas tank, plastic well liners, and popped out the tail lights.

There isn't really a whole lot of water in the wheel wells, just a few drops here and there, mostly (I think) from the condensation.

The gaskets around the tail lights are old, but my garden hose testing seems to indicate that they are holding up fine. All the same, I have removed them, cleaned them off, and am spraying them with a little flex seal to coat the gaskets to 'beef them up'. I'll reinsert and then check again. https://www.getflexseal.com/

Thanks again,

Packman

__________________
83 240D - 4 speed manual - Manilla Beige
189K miles, Tachometer mod, cool wooden shift knob from PeachParts, CocoMats, Original factory paint, manual windows, manual sunroof. Starting to add AudioWrap to this car too!

THe area between the trunk lid and the rear window tends to rot out due to old window seal on rear windshield.

__________________
Closing the store
Benzbonz.biz on your smart phone or tablet.

Save all those desiccant packets from pill bottles and chuck them in your trunk?

Baby diapers are also very moisture absorbing maybe pull the absorbent pack out of several set them strategically in the trunk see if the swell up?

This is such a strange problem to me because all the moisture in the air where I live falls to the ground as snow. I swear Alberta is dryer than a desert in winter.

__________________
Cheers!
Scott McPhee

1987 300D

I put a box of damp rid ,and change when needed

__________________
1999 w140, quit voting to old, and to old to fight, a god damned veteran, deutschland deutschland uber alles uber alles in der welt

It might be tricky to figure out a good way to accomplish it but if absolutly no leaks is certain. Insulation is one way. Some form of forced ventalation might be engineered in as well.

First though make sure what you are experiencing is what it is. This should be easy by just checking other cars in your vicinity. This effect is somewhat unknown on the east coast of Canada to the best of my knowlege. Although the principal moisture showing on the underside of the trunk lid is more typical of condensation as you mention than leakage I would suspect.

There was another thread on this a month or so ago but it tapered off inconclusive. I seem to recall that the OP on that one wasn't in the PNW.

There are several usual answers for moisture in the trunk, but the part that baffles me is the condensate effect on the trunklid.

That suggests that you either have standing water in the trunk, which apparently you haven't, or somehow moisture is being drawn into the trunk from outside and rising to the trunklid. I associate condensate with either pooled water reacting to temperature, or moist air movement.

Uber-weird and I can't offer any explanation... unless it's a generalized problem of all the seals being old and allowing moist air to enter, through some vacuum effect when the car is moving?

I had a serious but generalized moisture problem in the trunk last fall and winter (everything in the trunk was damp but no pooled water), but only slight condensate on the trunklid. All I did was to carefully clean around the trunk seal this summer and I left the trunk open in direct sun a couple of very hot days and 'massaged' the seal in one spot where it had deformed slightly. The sun seemed to help straighten it out.

Anyway no problems so far this fall.

The area where I live has the opposite problem to where Scott speaks about... we have very high humidity levels most of the year (and I live in a particularly bad spot that doesn't improve matters).

__________________


Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

Other sources of leaks:

1. Trunk lid star - 13mm bolt to remove star and inspect.
2. Trunk lid emblems - holes on each side holding down the emblems. Tiny grommets holding emblems in place may have fallen off.
3. Antenna mast seal - there are two, outer and inner.
4. Quarter panel moulding fasteners - if they go bad they can allow moisture inside. There is a maybe 8 or 10mm bolt at the corner of the quarter panel holding this trim piece to the car.
5. Tail light seals and seals under tail light
6. Fuel filler neck seal - allows water into trunk if not sealing properly.
7. Trunk lid "stops" on either side/rear corner of trunk lid

If water gets in and pools, when ambient temps go up the water collects on the inner surface of trunk lid.

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)