Real cause of leaking vapor barrier

[lesguy]

Until the "entry point" of water is not addressed, it will always leak into the cabin when the vapor barrier detaches from seal degradation. Water enters from locations shown below (BMW seals here have gaps). My solution:

1. Restrict the entry point by applying black silicone sealant (I used RTV108) or equivalent. (Yes, for those that have 4K eyes, I ordered new quarter window seals, but problem will remain).
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Sealing job not complete, but image below for illustrative purposes of where to add sealant. Place a piece of tape for the movable window before applying sealant.

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2. Re-Direct water away from barrier: I used a standard 8.5 x 11 plastic sheet protector, cut a small hole at an approximate area where the door handle cable will feed thru. Then get some of that remaining sticky bmw vapor barrier sealant and use it to place the plastic sheet underneath the door. This will re-direct water away from the barrier. I also used some sealant around the hole where the cable feeds thru the plastic sheet. (Note, make sure the plastic protector opening faces down!)

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...at the end it should look like this:

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3. Re-apply sealant and install vapor barrier: Remove any non-sticky sealant and re-apply new sealant. Install Vapor Barrier, reinstall door panel as required.

Total Cost: Under $1.00 for plastic sheet protector (any plastic cut to size will also do) plus cost of sealant. Labor: under 30 mins for each door).

Cheers!

Nice writeup. I believe the biggest positive impact is the plastic sheeting install to redirect. In my experience, the small holes you sealed outside on the trim corners arent the sole source of water coming into the inside of the door/backside of the door panel. I actually (as a test) applied a bead of silicone across the entire horizontal length of that edge for the entire length of the glass. Just as a test. Didnt put the window down. Let it dry. Then used a hose to pour water down that side of the car. Water still made it down to the plastic door sills.

Only thing that worked for me was to use a small propane lighter to really heat up the existing butyl. Then apply the vapor barrier with hard, firm pressure all around the warm gooey butyl. Hairdryer/heat gun method didnt get the butyl warm enough when I tried that method.

[rbelton]

I went with the OEM butyl tape and vapor barrier to repair water leaking into my ZHP



Link: https://youtu.be/QrYU1ImOqVM

[StephenVA]

Yep, The E39 are even easier as the wood trim can stay on and our interior handle stays on.

[Manny G.]

I'm just going though doing it again.. this time i spent about 10 hours removing the old butyl sealant cursing out whoever designed the door drainage for the E39.

I hate butyl.

I tried to heat it up with a heat gun but it just got more and more gooey... great if i wanted to reapply, terrible to remove it. Found a trick by frequently wetting it which would cool it down, then constantly tacking it with an old piece of already removed butyl helped pull it off the paint without damaging it. I suggest holding the butyl blob with something like a thick plastic bag so that you're not fighting against your fingers.. the stuff gets really sticky the more u dab it.

I got fed up with how quickly butyl was releasing its seal from the door and vapor barrier and decided to get rid of it all together. I bought new light gray version vapor barriers, and went with using Dap Dynaflex 230 clear with a caulking gun. The down side is that curing time is about 7 days. I will leak test it in about a week to see how it goes.

[Manny G.]

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Back to share some updates of what I did. The Dynaflex 230 failed. Parts of it never cured correctly and it rained a little during the curing time which caused the uncured Dynaflex to become a white watery substance. I was easily able to strip it all off and went back to square one to do the method shown in the pic quoted above, except i used 6mil HDX plastic sheeting which is also suitable as water/vapor barrier instead of the clear document binder sleeves. I picked up the shortest roll at Home Depot for about $25 bucks, contains PLENTY of material.

I mocked up some cardboard templates of the opening, the lower one also, and attached the sheeting similar to the picture, except on the top half of the sheet is stuck to the door from the cabin side, and the bottom half is stuck from the window side so that water from any angle will drain out. Its rained pretty heavy here over the last few weeks, and I left the car with nothing but the plastic sheeting just to test... not a drop in the cabin came through the plastic sheeting. I could see water droplets on the other side inside the door.

There is a hole for a door panel clip at the front of the rear door, the middle hole, that water did find its way through a little bit, ... I'll end up plugging that with a rubber grommet and skip using the door panel clip.

I used butyl to attach everything again because I enjoy torture.

[DashingDan]

I joined the forum because I had the same problem with my wife's X3. I hope my experience will help others.

Problem: leak in back driver's side door.
Result: soaked floor board.
First four repair attempts: reseal vapor barrier with new butyl.
Result: failure after about three weeks each time.
Next try: remove interior panel and vapor barrier. Seal the corner edges on the movable window wiper. I thought that would fix the problem. It didn't.

I had the wife run the hose on the windows and door. We found the trim seals were failing around the fixed window behind the movable window on the door. We saw a debris trail where the water was running down inside the butyl seal straight to the bottom of the vapor seal, where it eventually compromised the seal. I used clear RTV silicon sealer around that fixed window and the leak seems to be fixed. The panel is not going back on until I'm sure the problem is solved.

I don't think you can fix the problem without taking the panel and vapor barrier off to see where the leak is. Until you pinpoint the area of failure you are wasting your time resealing the vapor barrier.

[DashingDan]

After letting the sealant cure we tried the hose again. There were other leaks and each seemed to find its way through holes on the inside door skin, to the area behind where the vapor barrier would be. Any leak to that area would probable eventually compromise the butyl seal. We cut pieces from 2 mil plastic drop cloth and glued them in inside the door to make dams as the guy did above. That directs all water ingress into the door cavity where it will drain. Then we glued pieces over those on the inside of the door. The problem is the butyl sticking the plastic on may eventually give way, leading to a vapor barrier fail. I am going to seal the window entirely shut with silicone just in case.

[mry82]

Thanks for sharing! I plan to check mine out this summer...

[Nyc Dito]

I don't think you can fix the problem without taking the panel and vapor barrier off to see where the leak is. Until you pinpoint the area of failure you are wasting your time resealing the vapor barrier.

I've done 2 BMW for a total of 4 barriers and only ever had to take off door panel. Just used some RTV wherever the original barrier had removed itself from the butyl used by the factory. Never had any leaks on any years later. May not be "correct" or pretty but its worked for me and many others.

[LarryBrown]

I've done 2 BMW for a total of 4 barriers and only ever had to take off door panel. Just used some RTV wherever the original barrier had removed itself from the butyl used by the factory. Never had any leaks on any years later. May not be "correct" or pretty but its worked for me and many others.

This really seems to be one right answer. Easy and quick, only uses minimum amount of the permanent silicone sealant that the butyl people want to avoid, and by addressing the vulnerable spots that get most/all of the abuse it's a permanent fix.

Because of a heretofore unheard of talent at procrastination, I've been running my E39 2003 525i for two years with the vapor barrier completely loose (rear left). I do have some Hefty garbage bags draped over the large holes in the manner prescribed by the guy above with the sheet protectors. I tried to do a good job with those but it actually looks pretty ragged. Because my parking space in the garage is temporarily occupied with two dumpster find computer server racks and a water heater that I need to install in the house someday, I've been parked outside for months and here in Houston, TX, we get deluges of rain regularly and I have not gotten a drop on the mat. That leads me to believe that the vapor barrier is not as critical as we think, since my car is working fine with the barrier just barely tacked on in a few places.

The door is an outer sheetmetal skin, an inner sheet metal lining, and a vapor barrier. One thing I can say with confidence, the majority of the problem is at the round hole in the inner sheet metal lining at the bottom front corner of the door. That corner is where the vapor barrier seal fails, meaning that's the corner that gets most of the water abuse, making that corner most vulnerable to continued water influx. I sealed that hole with some black Gorilla tape on the inside, and some clear water proof tape on outside (facing the passenger compartment). I used clear on the inside rather than apparently beefier black so that I could inspect the Gorilla tape and see how it is holding up. The Gorilla tape is holding up perfectly and no water can penetrate there and that seems to have solved my problem.

On any repair of the vapor barrier my experience recommends sealing that hole with waterproof tape.

For those non-Houston readers that may not know what Gorilla tape is, it's a plastic tape similar to duct tape that is supposedly useable in wet conditions and is widely available at any local stores like Home Depot, Lowe's, and Wal-Mart. It has worked for me in this application.

Early on I was on the "we *must* find the reason for the water entry" crowd, and the "it's a *vapor* barrier, not a *water* barrier" crowd. Then I saw a guy on youtube test his door with a garden hose and I was shocked to see water simply *pouring* into the door compartment. When I saw that I realized that these doors are not designed to keep the water out. They have given up on that as impossible and instead just deal with whatever water gets in.

[mry82]

^Thanks Larry! That seems like a series of good observations and ideas.

[Manny G.]

Finally remembered to transfer the photos of what I did to remedy this. There has been 0 leakage since.

Note the transition of the vapor barrier sheeting from outside to in,.. the butyl i used also transitions and this helps direct all of the water outwards.

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[jlce10]

I encounter the vapor barrier leak lately, after going through youtube for an easy fix, it did not solve the problem by just sealing the vapor barrier. I read up this post and found alot of helpful guidance. What I conculde after trying all the above.

1. sealing the vapor barrier does not help because the leak comes in from other holes as well. (read on for clearer explanation on this)
2. sealing the quarter window frame does help abit by preventing alot of water getting in but does not solve the leaking issue, it still leaks but lesser.
3. Changing new VB at the bottom of the window does not help as well.

I then remove the vapor door panel and hose the window to check the leaks, apparently its leaks through a few holes and the bottom hole into the vapor barrier, the water have no place so escape and then leaks through the vapor barrier seals at the bottom and into the door panel.
I solve it by having a plastic sheet to direct the water to the bottom of the door like one of the member did and seal up all the holes with gorrila tape. Problem solve! One very important tip is that the seals for the vapor barrier have to be water proof tight.

I hope this helps everyone who encounters this problem in the future!

[rdl]

I too have suffered the wet rear floor misery ... time after time after time.

In all cases for me, the leak path into the rear footwell was a failed/separated seal between the barrier and the door's flange. None of my leaks have been via various holes for clips etc. or the quarter windows. I've confirmed this by flooding the outside of the door window with the trim panel removed and observing water appearing at the bottom of the barrier - on the inside, of course. I've also discovered that the seal around the barrier is absolutely necessary. When I removed both the trim panel and the barrier, then flooded the rear window, water inevitably seeps past the "wiper blade" seals and drips off the bottom of the window. These drips fall to the inside of the inner door panel due to the "lean" of the door configuration. Plus, the water actually falls onto the barrier and then tracks along the surface to the bottom of the barrier - it never drips off the barrier to the bottom of the door cavity. If the barrier seal leaks, this water winds up in the rear footwell. And that seal always released over time; sometimes months, sometimes a year & a bit.

However, in the last instance, I seem to have found the, or at least a, reason for prior failures. I realized, finally, that I'd always installed the barrier pulled sort of flat to get the maximum overlap between the barrier and door panel's flange. Further, I realized that the door pocket in the trim panel protrudes inside the door into a depression/cavity molded into the barrier. With some rough dry fitting it seemed to me that the pocket was pressing against the barrier. And that constant pressure over time was probably pulling on the butyl seal and causing a separation over time.

So last time I reduced the overlap so the barrier was more slack & the depression for the pocket was further outboard, i.e. more room for the pocket to protrude into the door cavity without stressing the barrier & butyl seal. I'm going on 3 years now without any more leaks.

EDIT: I should have mentioned. I placed the butyl rope so that its edge is ~3/8 " from the edge of the metal flange. I then place the barrier so that its edge is ~3/8" past the edge of the butyl. This on the lower half of the barrier. The upper half isn't so critical since the drips off the window strike the barrier lower - the seal there is more for sound and draft/wind noise control. Besides the door trim panel isn't stressing the barrier as the pocket does.

Not that I don't regularly check the rear floor after every rainstorm. A learned response peculiar to E39 owners, I think. LOL

[rlordjr]

Yep. If you check every time you'll feel moisture even when there isn't any. Sort of like ghost pains in an amputated limb I guess.

[Mike WW]

I'm in the butyl camp, IMO done right it works well. But on the silicone caulk, how does the seal come off afterwards? Is the vapor barrier reusable? With the famed window regulators, among other things, I kind of expect to have to get back in there sometime.

[John Bowman]

I had water on the passenger rear of my E60, reapplied butyl sealant to both rear doors. When I removed the driver side VP it tore and had to get a new one.
One “trick” (if you want to call it that) to get the best seal was to peel as much of the butyl tape as possible, it’s messy, wear gloves, next I heated it with a Harbor Freight hot air gun and peeled more using paper towels then when there was not much left I used mineral spirits to clean what was left, it will not damage the paint or the clear coat. I was left with clean surface to apply new tape. I used a little thicker diameter roll, installed the VP and heated the butyl bead till it got soft and gooey and pressed it into the door. Be careful not to heat the VP too much. It’s been five years and I had some separation at the top rear VP but the rest looks like the day I applied well stuck on and sealed. One draw back is that if I ever need to get into the door I think will destroy the VP peeling it.
A bit labor intensive, messy, but I got a great seal.