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Trunk Taking on Water

7K views 34 replies 17 participants last post by  LWB250 
#1 ·
The trunk in my '89 560SEL is taking on water in the rain and it's got me stumped. There was a little water coming in from the taillight lens seals but I have cured that. The main issue is a drip coming from the front right corner. I have put two good coats of sealant all along the fine line between the perimeter seal and the body across the front and side edges, figuring water must be building up and sneaking underneath the seal, over the lip in the body, and into the trunk. It rained much of last night so I took a look this morning and there's still a large puddle in the right side (I have the carpets removed so I gauge it clearly). Again, it's not just a little water but quite a bit. Any thoughts on where it can be coming from? The passage is perfectly clear for the water to drain down the sides. My only thought now is that the seal isn't pressing against the lid well enough anymore and that what water can is running underneath the lid and straight into the trunk instead of being stopped between the seal and the lid. I'm not sure that basic physics would allow much of that but it's all I can imagine right now. Eager for any input. Thank you!



 
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#4 ·
The trunk seal is glued on so, unless there is glue separation I dought it's coming from under the trunk seal. If the rear window glass gasket is not leaking, then the trunk seal needs to be replaced for sure. I recently had mine replaced and no more water leaks.
 
#6 ·
You can buy a creaping crack sealer to put on the rear screen rubber ,like let it drip on the glass and lift the rubber seal so it gets in side the seal .Try a caravan or trailer dealers .Its used for sealing the joints of roof to the alloy rails on the caravan roof. It comes in a couple of colours ,white and clear .Makes a mess if it rains before it is dry .But easly removed with white spirits. I do have a tin of window rubber sealer made by Coma Seak And Seal but i dont think its made any more.
 
#7 ·
Thanks for the input, all. I'll investigate again but I did look/feel to see if the water was originating from somewhere towards the front of the car, like the rear window seal, but I couldn't find any indicator that it was.

Anyone know if the $25 Uro seal is any good?
 
#11 · (Edited)
Back in the 90's I had a 1985 500SEL it was eight years old when I bought it and kept it for eight years. That car had no problems ever with the rear glass leaking during my ownership. I do know that my 500SEC had a leak from the rear glass due to the rubber seal. The water gets in there and rusts the lip the seal fits onto and eventually starts to leak into the trunk. I had to replace the panel just below the rear glass when they replaced the seal on that car.
I'm not sure but I think the SEL is less likely to have rear glass seal problems, in my experience the C126 is the model with the rear glass leakage problems. I could be wrong I suppose.
I don't think URO could screw up making a trunk seal. It's the more sophisticated stuff I wouldn't touch with a barge pole.
 
#10 ·
I would strongly suspect the window.

I'm guessing you have some rust at the lower corner of the window. Get in the trunk with a strong light and very flexible body and look all around that area. You have to crane your neck to see through those holes that go across the back of the trunk under the window. Also look above the wheel well at the window area there.

I think if it was your trunk seal, you would have figured that out by now. Do you have a trusted assistant? Lock them or yourself in the trunk and have someone run water on the car in the leaking area.

Another thought: Doesn't the sunroof drain down through the C pillar? Maybe you've got an issue there.
 
#15 ·
If you buy anything other than an MB seal for the trunk or the window you are foolish and should just sell the car now. Brash statement - you bet. Get a can of 3m adhesive remover and a plastic trim tool. Get the 3m remover lightly in the gap between rubber and trunk steel. Go around the top curve left to right. By time you are done take your trim tool an gently begin to separate the seal from the metal, using more 3m remover as you go. 8-15 minutes will loosen the adhesive. You may want to get a tube of black adhesive from 3m as well, this is going to be needed anyway. As the remover evaporates, the adhesive is tacky and re-energized as new. Apply new bead to the rubber where it clearly meets trunk steel and let dry 10 minutes. Clean trunk channel with adhesive remover so that it is free of debris and if you have rust that needs to be stopped and treated. When trunk is clean and ready for seal, wet both seal wet with the dry glue and the channel of trunk with 3m adhesive remover, activating the tack of the dry seal. Without stretching the rubber, seat the rubber and let dry fit 1/2 hour. ( disconnect the wires to the trunk light or switch when you begin all of this)

I have installed 4 doors, trunk and back glass. All leak free and all MB Rubber.


As for back glass. Mb does not use pipe dope anymore on the window. I used the required mb sealant in the window channel and it is a poly that never really hardens up but isn't tacky. I then placed a bead between outer glass and rubber seal. I had help from Safelight vendor.
 
#21 ·
I have installed 4 doors, trunk and back glass. All leak free and all MB Rubber.
So it's not too hard to remove the glass without breaking it?

Is it possible to remove the existing seal and re-use it?

-J
 
#16 ·
I'll 3rd the rear glass seal and don't waste your time and money on anything "URO". From experience here have a look/feel in the boot just forward of the lid on the underside where the glass is there are a series of holes in the panel, feel and or look up in there for any moisture or rust. If you do then likely the window seal is leaking, common problem.

There is a rather easy, though tedious, fix you can do, it worked on mine. Give it a day or two in a heated garage if you can or at least out of any rain. Get a tube of black RTV with the screw on plastic nozzle, cut the second notch and flatten slightly. Now here is the tedious part, use a popsicle stick or similar to lift the edge of the rubber to get the nozzle in at the paint and run a bead all the way around between the rubber and the painted metal and then another bead all the way around between the rubber and the glass, don't worry if any oozes out it can be cleaned up once it "skins" and sets a little. Next, up in the holes on the underside give some short bursts of either primer or color paint (rattle can), have the carpet out just in case. I did this to mine just after buying her two years ago, noticed a puddle in the boot after a rain. Since then it's been dry as a bone inside
 
#17 ·
I discovered that the leak is indeed coming from the rear window seal. I'm saying this based on how I got in the trunk while an assistant used the hose (let's face it, I'm probably not the first body in the trunk of an S-Class!) and I realize that although the drip is immediately under the trunk seal, it's actually traveling down the body seam that's there and originating immediately under the rear window seal. I packed up that corner with sealant. It seems to still leak after a rain but in fairness it A) was noticeably better and B) was a rainstorm unlike one I can recall in recent memory. I'll take a look after a "normal" rain and see how we're doing.
 
#19 ·
Read my post #16, the sealant was a good idea but sounds like it's wicking around the "packed corner", to ensure a good seal you'll need to go all the way around
 
#20 ·
It is ALWAYS the rear window seal.

The SDL has a trunk leak, the SD has a trunk leak, my 220D had a leak, even the stupid S430 now has a leak that came about after the car had body work due to some idiot hitting it while it was parked.

I will need to replace the rear windows in the W126 car, sell the W220 and never again purchase anything newer than 30years old.
 
#23 · (Edited)
If we are talking back glass, you are simple to remove. However, the inside rubber lip is so thick, you are sacrificing the rubber there to remove the glass. Unscrew the defrost connections at c pillar. Use razor knife under seal and glass, cut along window, as you are removing outer lip.

Outside using dumbbell style suction centered vertical, but top end slid inward, create a two hand hold. Push in firmly but this is glass, albeit robust. You will then grab both handles of holders and rock it in and out until you lift up and out. It's big but a one person job if you plan. Prelim work, have saw horses ready covered in moving blankets pretty close together, like 18". Store glass curved side up to catch water so it won't crack. I have done two or three removals and one install of back glass. If original, it is the rubber holding glass, and the rubber floats on the chassis cut out.
 
#25 ·
The approved MB installer from safelight used my MB goop for the channel, and also under the seal/glass outside.
 
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#28 ·
Me too, caught the problem pretty early on my SE but the lip was gone in a couple of places. Fixed properly, new MB seal after too etc.
The SEC is more prone because of the screen angle. In the UK we pretty much have to assume it'll be rotten there.

Ps, I know we all know this, but I'm just going to put this here for future readers - be sure to use automotive sealant, never the bathroom kind which will cause catastrophic rust due to its chemicals/salt or whatever.

Putting a windscreen in my other car recently I found an excellent sealant which is like black goop just for windscreens etc. It's extremely sticky and stays soft. So much better than any silicone based product which would be a lot more temporary really.

I used silicone on my SEC and it did slow the leak for a time. Didn't last very long really though, a year or two I guess before my boot was an aquarium again.
 
#29 ·
Here is the modern MB PRODUCT for the back glass:

 
#30 ·
Updating this old thread in case it helps someone in the future. There was a little water coming in from the lower right corner of the rear window, as described, but in the end it was actually the right vent under the carpet that was the main issue. There are these little tabs that stick out of the seal, and it appears someone had the vent out and then put it back in but got one of the tabs stuck in between the vent and the body, which caused it to not seal at all. I couldn't really get it out to fix it, but I caked on some weatherstripping sealant and I'm 100% dry now. You can test this by spraying a hose on the fender/quarter panel. The water just pours in from behind the exterior trim panel if it's not sealed well.

The taillight seals were also an issue, on both sides. I sealed those up, too.
 
#31 ·
I have a new trunk seal, and likely won't put the new one on before painting the car but what sealer do you recommend to put the new seal in with? The old was some sort of yellow glue that had hardened with age. My guess is you put a bead all around the trunk metal, then install the new seal. There should be no gap anywhere around the trunk metal where water could get under the new seal, correct?
 
#32 · (Edited)
I do all my seals with 3m black adhesive. I use it in conjunction with the 3m adhesive remover. Have you ever fitted a trunk seal? Only use MB ($$$) and it is perfectly engineered to fit. I will write up how to do this fool proof the first time if you like.



Correction SEE POST 15 for the write-up.
 
#35 · (Edited)
Some things to consider when replacing the trunk seal, something I have done on a number of different MB models:

1.) ALWAYS use a OE brand seal. Despite the idea that "anyone can make a seal", it is a highly engineered part that has all sorts of little details on it to make absolutely sure it works. The quality of the material is critical as well. How long did the one that's on there last? Yeah, now you know what I'm talking about.

2.) Make sure the seal channel on the body is surgically clean. Use a dull popsicle stick or other piece of flat wood, and with the channel flooded with 3M Adhesive Remover, scrape until every last bit of the old seal and glue are gone. I dam up the ends of the groove with some putty or a rag so the 3M Adhesive Remover will stay for a bit. You'll probably have to pour some in, let it soak for a few minutes, then rinse, lather and repeat, so to speak.

3.) Put an old sheet or tape masking paper over the back window area down to where the trunk opening begins. Why? The seal is going to have to be placed over the trunk lid AFTER the adhesive is applied. This prevents you from getting adhesive on the window and painted surfaces around it.

4.) Use 3M black weatherstripping adhesive, NOT the yellow stuff. You have to apply it to both surfaces, so lay out some towels or paper on the floor next to the car to put the seal out. It has some curves in it that will make it twist, but don't worry about this. Put a thin layer of sealant on the bottom edge (the bottom of the "U", if that makes sense) of the seal and a similar amount on the bottom of the seal channel on the car. Don't put it on the sides of the seal or channel.

5.) How the heck do I know how to put this thing on the car???

Before you start, look at the seal closely. Under the lip in one location you'll see the Mercedes part number molded into the seal. This goes at the exact center of the trunk opening on the trailing edge, that is, just above the license plate or trunk lock cylinder. Pay no attention to where the seams are in the seal. It's not relevant to the installation - the part number IS. The "C" shape of the seal should have the opening of the "C" always facing out.

After the adhesive is in place and has tacked up, start at the center above the license plate where the part number goes and gradually work around, a little on each side at a time. DO NOT stretch the seal as you put it in place. As you get closer to the top center you'll have a good feel for the tension on the seal. You shouldn't end up with any excess or a "crimp" by the time you get there, or you have stretched it.

6.) Once the seal is in place, go around with your fingers and apply pressure to it all the way around the trunk opening. Make sure it's sitting upright in the channel and not cocked or angled. Once you're satisfied that it's in place, close the trunk lid and leave it that way overnight.

Dan
 
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