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Fixed your leaking vapor barrier? Don't forget to lift the carpet.

40K views 23 replies 16 participants last post by  540 M-Sport 
#1 ·
BMW uses a high-density foam backing that is bonded to the E39 carpet. It's a great noise insulator, but it also acts as a giant diaper when the vapor barriers leak.

So, if your rear carpet feels damp to the touch, it's actually saturated with a shocking amount of water that is held within the foam.

Once water gets absorbed into the foam, it's impossible to dry without lifting the carpet.

There are several bundles of electrical wires under the carpet, so I think it's beneficial to thoroughly dry the foam backing.

Start by removing the back seat. Then the rocker trim. It uses a 10mm bolt with 2 push-in fasteners (be gentle.. this piece is brittle)

Then I popped off the bottom of the B pillar cover. This allows the carpet to be folded back and lifted up.

I've spent over 2 weeks placing absorbent ShamWow towels (made in Germany. You know the Germans make good stuff) under the carpet overnight, wringing the excess water, letting the towels dry, and repeating the process again and again.

I've pulled out so much water that it makes me wonder how many electrical problems could be attributed to wet carpets.
 

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#2 ·
I think you are right, mine leak and are on my list to fix. I put a piece of aluminum foil on the door jam so it extends inside 3" and under the door 3" then close. I have towels on the floor and they dont appear to get wet any more. I put a dehumidifier in my car overnight on high and in the AM, things are pretty dried out inside... now I need to jump on these, driving me crazy. Did you use the weatherstrip "bead" or 3M Weatherstrip Adhesive (Yellow) approach?
 
#3 · (Edited)
I purchased a roll of Butyl adhesive (that's what the factory uses) from a local auto body supply company. It sticks like crazy on the door, but I had issues getting a secure bond on some smaller areas of the vapor barrier. I think that the process of removing the barrier, and the old Butyl, slightly delaminated the surface of the barrier. If I ever need to do this again, I'll order new vapor barriers (about $35 each) to insure clean bonding surface.

PS: A quick way to check your vapor barrier is to remove the Puddle Light and stick your finger inside. The panel will be wet in that location if the barrier is leaking.
 
#4 ·
For $35@ probably not a bad idea, do it once, do it right, never do it again. I'm thinking of picking up the BSW stage 1 speaker upgrade kit as well and swap out the stereo speakers at the same time... again, dont want to open up the door again while I have the car (the PO replaced both rear window regulators, hence why I suspect they leak).
 
#5 ·
Two things:

1. The Vapor Barrier: I think you can use any thick plastic barrier at hardware store. This is the same stuff people lay on the basement gravel before pouring concrete floor. Make sure you get the thicker plastic type.

2. The butyl roll: I got a roll from a local Auto Glass Repair shop: 15-foot roll for $15.
The roll is the same size as the pencil (about 3/16" in diameter). Go to any local Auto Glass Repair shop and ask for it. This butyl stuff was used in American cars from 1970s and 1980s Chevy etc. It looks like this:

 

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#8 ·
The E46 crowd is having trouble finding the right sealant according to this post today:
I have redone all 4 doors vapor barrier seals twice now. I used the 3M window-weld in a roll which is exactly what the dealership told me to use. Apparently its what they use to do the job as well. The first time I redid the seals they leaked and I assumed that it was because I hadn't pressed down hard enough to obtain a good seal. So this most recent time I used a small paint roller to roll over the fresh bead of window-weld on each door to be sure that I got a good seal. I checked each of the vapor barriers right after resealing them and all of the seals looked good and held when I tugged on them even moderately. I thought that surely I had solved the problem. Not so! The doors have now leaked again, all four of them. It has rained here in the south-east for about the past 7 days straight so I have some pretty soggy floor boards on all four corners. I am going to reseal them again this weekend using silicone sealant as I am about 99% sure it will work. I will just loose the ability to simply pull the vapor barrier off if I need to get under it at a later date. Does anyone have any other suggestions as to what to use before I use the silicone sealant? I am sure it is the vapor barriers as I have taken the door panels off and watched the water run out from behind the vapor barrier and into the car where the vapor barrier has pulled away from the bottom part of the door.
 
#11 ·
I did mine a couple years ago and found out recently that both doors are leaking again. I used the 3M window weld last time and wondered about trying something else this time, like this...

Anyone tried this:



I heard really good things about it. Seems like the windows shop have it. (3M 08609) I also found it on Amazon
I wonder if this creates a more permanent bond? I'm heading out to Auto Zone to check that out or buy the window weld.
Why not just use regular old silicone caulking?
Silicone makes a more permanent bond and you want to avoid that in order to reuse the vapor barrier.
 
#10 ·
Why not just use regular old silicone caulking?
 
#12 ·
Resurrection

I've used almost a whole tube of 100% silicone on my vapor barriers
When I redid them. I used tape to hold the barrier tight and let it cure for almost 4 days.


It did stop the leak however when it rained a lot, I did have a slight wet towel smell but no wet carpets.

Fast forward a year later and I'm doing a window regulator. The silicone did not bond to the vapor barrier. Seemed it had a minuscule bond, It peeled it back like weak masking tape peels off things. I did not gave the hellafied bond I hoped for on the door either.

I did clean the old stuff off and used mineral spirits and dried real good before I did it also.
I left some parts with the old butyl residue and it seemed to grab there a little better.

Maybe I sabatoged myself with the mineral spirits the first time.

Going with window weld and butyl this time.
 
#14 ·
Resurrection

I've used almost a whole tube of 100% silicone on my vapor barriers
When I redid them. I used tape to hold the barrier tight and let it cure for almost 4 days.

It did stop the leak however when it rained a lot, I did have a slight wet towel smell but no wet carpets.

Fast forward a year later and I'm doing a window regulator. The silicone did not bond to the vapor barrier. Seemed it had a minuscule bond, It peeled it back like weak masking tape peels off things. I did not gave the hellafied bond I hoped for on the door either.

I did clean the old stuff off and used mineral spirits and dried real good before I did it also.
I left some parts with the old butyl residue and it seemed to grab there a little better.

Maybe I sabatoged myself with the mineral spirits the first time.

Going with window weld and butyl this time.
I just did my RR door. I used 3M Black silicone adhesive, guess it's for weather stripping and what not. So far so good. 2 or 3 rain storms bone dry. need to do the LR door. I've never noticed this issue on the front doors. Do they suffer from this lack of F'n design also? I need to pull the carpet up and check for water, but I removed the floor mat and in 120 degree FL Sun days, 10hrs in the parking lot, day after day pretty much dried everything out that I could feel.
What I discovered to be the problem causing my second leak was the broken white plastic, (not sure what to call it) snap-locking, push/pull "clip." Since one of mine was broken and did not block the corresponding hole, the water poured in through that opening. I blocked it using the 3M butyl tape and have not had a problem since.
There are plenty of tips on how to do this DIY, and another helpful idea is to use a heat gun on the butyl tape before putting on the vapor barrier.
Here's a thread depicting what I just explained above:
http://www.bimmerfest.com/forums/showthread.php?p=7431750#post7431750
Good luck!!! :thumbup:
 
#13 · (Edited)
I just did my RR door. I used 3M Black silicone adhesive, guess it's for weather stripping and what not. So far so good. 2 or 3 rain storms bone dry. need to do the LR door. I've never noticed this issue on the front doors. Do they suffer from this lack of F'n design also? I need to pull the carpet up and check for water, but I removed the floor mat and in 120 degree FL Sun days, 10hrs in the parking lot, day after day pretty much dried everything out that I could feel.
 
#16 ·
For the cross-linked record, a similar question came up today asking what length of adhesive bead to buy ...
> E39 (1997 - 2003) > how much vapor barrier seal
Going to the dealership tomorrow to get some vapor barrier seal, they are selling it to me by the metre ($9 per metre) and was hoping someone would know the approximate length required to do the rear doors
You could measure around the door panel and figure it out.
I'd say 2.5 meters/door shoud be enough.
3M Window weld. 1/4 0r 3/8 box is inexpensive, not messy and easy to use
 
#17 ·
Hi guys,

Apologize for resurrecting this thread but the time came to have my own pond on rear passenger footwell.

In preparation for tackling the issue I bought new BMW sound dampeners, cause I can't really call them vapor barriers :tsk:. They are very,very flimsy ... Can't imagine how that thin foam would prevent the water coming in. I need to handle them like raw eggs.

So I bought some real vapor barriers from Home Depot, 152 micrometers thickness. My plan is to use the Home Depot product to seal against water then apply the BMW sound dampening foam over it.

Has anyone tried his before ?

Thank you

PS. As the sealer I intend to use the 3M 08609 - window welding urethane.
 
#18 ·
Here is the rear left door with Home Depot vapor barrier applied (still need to trim the edges once the sealant is cured).

One thing I like about using the vapor barrier vinyl is that you can easily check whether you've applied the calk uniformly and truly sealed everywhere. The pitfall in this case however, is making sure you have left enough slack at the bottom for the concave part of your panel (at least I hope I did ... :rolleyes: - I'll know tomorrow).

Am am still waiting for the sealant to cure and then I will apply the sound dampener on top of vapor barrier (if possible). As I do not need a sealant anymore, I am still debating what type of glue I should use for this step. I think I can attach the dampener only on a few spots.
 

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#19 ·
This question came up over here today ...
> E39 (1997 - 2003) > What's the NEXT step for removing the door panel to diagnose broken window regulators

My vapor barrier was glued with some silicone substance. What's for? For noise reduction? Do I need to re-glue it?
The substance is butyl. It prevents water from passing. If you do not reseal the vapor barrier, you might get flooding under the carpet the next time it rains heavily on your car. Sealed barriers also mitigate fogging of the inside and reduce outside noise. Resealing is imperative on a rear door since flooding is almost a certainty there
Old butyl cannot be reused. It should be removed. First by a skilled application of force and then cleaned off with gasoline. You can then apply fresh butyl cord or one of the newer rubberizing compounds. Apply only 10N of pressure over thumb sized surface of vapor barrier to properly seal fresh butyl.
See also:

- Vapor barriers: Sealant for door panel vapor barriers (1) & sizes for the adhesive (1)
 
#21 ·
Just went through this and thought id ad some ideas based on what i researched and what i did.

1. First, you need to understand that the rain is meant to penetrate between the window glass and the window trim and go inside the door cavity. It is then meant to fall to the bottom of the door cavity, and go out the holes in the bottom of the door. This is by design. There are way too many people online who think the water is meant to NOT go inside the door frame, and start applying silicon and all sorts fo other crap to the window edges to prevent water penetration.
2. Given that Butyl didn't work the first time, i find it hard to understand why people would use it again. There are numerous posts on multiple boards of people using butyl again and having it fail. Again. It would appear for the long term reports that i read that the best option is to abandon re-using the barrier at any time in the future, use silicone to weld the barrier to the door, and then use outdoor adhesive tape (like roofing tape) to tape the edge of the barrier to the door frame. So you have both the silicone and the tape forming a barrier. This seems to be the most successful option i have seen online.
3. Most people dont have a paint dryer etc in their garage and most people dont want to remove seats etc and pull out the whole carpet. Instead, here is the solution i used after watching a lot of videos and a little trial and error. Park the car on a sloped driveway or jack up the front of the car. The steeper the better. All the water in the carpets will slowly flow to the back of the carpeting just in front of the rear seat. Then mop up any standing water with a towel and move to step 4.
4. Heres the key. You need to move the front seats as far forward as possible, remove the rear seat, lift up the carpet, keep it propped up with some wood blocks, and then start using a hand on top and a hand on the bottom underneath the carpet to apply pressure and squeeze water out of the foam that is laminated to the bottom of the carpet. Keep sopping up water on the metal floor as you go. Do this until almost all the water is out of the foam and it just feels wet to the touch.
5. Place a Vornado or similar ceramic heater on the metal floor of the back footwell, with the carpet propped up with wood blocks, and direct the hot air under the carpet and at the foam. I tried just using a fan, as this had worked in my flooded house. However that was literally taking forever. The heated air made the process go much much faster. Crack the windows a little to let the mosit air out and close the doors and let the heat do its job. An alternative that i have seen is to just turn the heat on full in the car, make sure that the footwell vents are blasting, and leave the car that way for a few hours. Just make sure you leave the carpets propped up so air can get under there.

I used this model for my E39 and it worked well, and only took a couple days for the carpets to dry out. So far so good on the fixed vapor barrier.
 
#22 ·
I still use the 3M Windoweld (butyl rubber sealant "rope"). There are two tricks to get it to work properly. One is buy a wallpaper seam roller to apply lots of pressure. Two is to heat up both sealing surfaces and the 3M Windoweld itself with a hair dryer. Getting everything nice and hot first, makes the Windoweld seal really well. If I do this, it holds for many years. If I get lazy or sloppy and not use the hair dryer and seam roller, it holds for less than a year.
 
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#23 ·
Another thing to add in here. If your rear door panels get even the slightest bit warped on the bottom where the barrier leaks. The panel clips won't seat properly and water could still get through. Best to apply a small amount of butyl around the clip holes to help keep things nice and tight.
 
#24 · (Edited)
I noticed on a one or two of my door cards, the plastic clips have a thin black "washer" that I believe is supposed to help seal it. I don't know what the part number is, I should look it up and buy a bunch. I do keep a bag of 6 or 8 spare of the plastic clips as they do break or get crushed if you are not careful. I have done the trick of applying a small amount of 3M Windoweld to the actual holes when I found water intrusion through one of them once. But I don't do it as a matter of course, only because it gets a little messy.

Just checked on Realoem and the thin black washers that fit between the door card clips and the door are not listed.
 
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