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Discussion Starter · #1 ·
Thanks to Lunker325 (Brian) for info on how to do this, I fixed my rear doors from the leaking water horror that some M5's suffer from. Very easy DIY. Mx5 is coming over next week to do some work on his car and mentioned he wanted to do this repair so I thought I would go ahead and get my car done so it will be easy to do his. We will be working against the clock on his car, so I wanted to do a trial run.

Remove door panel (One screw on door handle, the rest is just pop locks securing the door. Take out the window switch and the flood light and unplug them.

Clean up area around old seal

Use some silicone to create a new seal (I used 732)

Tape up seal until it cures

Let car air out (I hate the smell of silicone)

Re-install door panel

Pics....

Visible water damage





Old rubber seal







I love blue tape



I know you are digging the power wheels in the background.....

 

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Soon VERY soon.
 

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Not sure what silicone 732 is and why you have all that blue tape holding the barrier on? What you need to do is remove the old barrier and remove all the original black 3M sealer which is extremely tacky and somewhat difficult to remove. However, once you discover how to remove it it gets easier. Once you have like a golf ball sized chunk rolled up you actually use that as a magnet to get the rest of the stuff off by "blotching" the old seal. Again, it's difficult and you need to repeatedly go over and over the old seal until it lifts off. Once you have the old seal off and everything cleaned up just place a new seal along the old path, on the door, not the barrier, as you will see where the old seal was as it contours along the door. You don't need a new barrier unless it has a tear or hole in it. Press every square inch of the barrier back on the new sealent and you don't need tape to hold it and it doesn't need to cure. This "732" stuff that needs to be cured, not sure you should use that. This 3M stuff, I forget the product # can be had at the dealer, or, I did see the EXACT same stuff at Advance Auto type auto parts stores. If anyone wants the product # I can look in the garage.
 

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Not sure what silicone 732 is and why you have all that blue tape holding the barrier on? What you need to do is remove the old barrier and remove all the original black 3M sealer which is extremely tacky and somewhat difficult to remove. However, once you discover how to remove it it gets easier. Once you have like a golf ball sized chunk rolled up you actually use that as a magnet to get the rest of the stuff off by "blotching" the old seal. Again, it's difficult and you need to repeatedly go over and over the old seal until it lifts off. Once you have the old seal off and everything cleaned up just pace a new seal along the old path, on the door, not the barrier, as you will see where the old seal was as it contours along the door. You don't need a new barrier unless it has a tear or hole in it. Press every square inch of the barrier back on the new sealent and you don't need tape to hold it and it doesn't need to cure. This "732" stuff that needs to be cured, not sure you should use that. This 3M stuff, I forget the product # can be had at the dealer, or, I did see the EXACT same stuff at Advance Auto type auto parts stores. If anyone wants the product # I can look in the garage.

2 things, first if Im reading your post correctly youre saying that you should use the 3M stuff instead of the silicon and its the same exact stuff they used to build the car. If thats correct, then isnt the same thing going to happen again?

Second, silicon is waterproof and Im pretty sure itll last ages longer than the double sided tape that youre referring to.

To each his own but when I do this and its going to be soon because I just found my back foot wells sopping wet, I want a permanent fix so I dont mind having to let it cure nor do I mind using the painters tape to hold it in place until its done so.

I may have read your post wrong. I appreciate you posting an alternative approach but to me I want something thats gonna last longer than it did from the factory. Silicon I know for sure will do that.
 

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2 things, first if Im reading your post correctly youre saying that you should use the 3M stuff instead of the silicon and its the same exact stuff they used to build the car. If thats correct, then isnt the same thing going to happen again?

Second, silicon is waterproof and Im pretty sure itll last ages longer than the double sided tape that youre referring to.

To each his own but when I do this and its going to be soon because I just found my back foot wells sopping wet, I want a permanent fix so I dont mind having to let it cure nor do I mind using the painters tape to hold it in place until its done so.

I may have read your post wrong. I appreciate you posting an alternative approach but to me I want something thats gonna last longer than it did from the factory. Silicon I know for sure will do that.
I think you read at least some of it wrong. I didn't mention anything about using double sided tape. I indicated no tape is needed to hold the barrier on while it's curing because using the 3M stuff requires no curing.Yes each into his own here but I think where the problem comes in here with this failure on the barrier is from previous work someone has performed while having the door panel off and not correctly re-installing the barrier. The 3M factory stuff is plyable and meant to be removed and re-used if needed. Example: if you need to remove the door panel for some reason and work behind the barrier you can carefully, slowly pull the barrier away from the door and place it back without issue. My guess is using the 732 stuff that needs curing would require a total re-do if removed? The factory stuff does not fail if it was installed correctly and it will never break down for no reason. I had an issue with my 2003 right rear door leaking and discovered the dealer never installed it back thoroughly. If done correctly and one takes there time to install it completely then this 3M product will not fail. Also, if you have "sopping" wet footwells I would remove or at least lift the carpet up back there where it was wet and let it dry out and maybe even spray something to kill any potential mold that may have grown under the carpet. Maybe I'm just being anal but thinking logically of at least what I would do.
 

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BMW has their own Buytl tape which is the correct way to repair this. Remove the door panel, remove the vapor barrier (do not tear/rip it). It's important to remove all the old butyltape next. Then lay a frash bead of ribbon sealer/tape around the area. You can use a heat gun over vapor barrier quickly, to get the tape nice and sticky. Re-install the door panel and you're done.

Silicone is going to be a major PITA to clean up next go around. Definately would not use this method.

Normally the factory tape fails, because whoever was last in there replacing a window regulator, etc. Didn't take the time to replace the tape. They just tried to reuse it, and as you can see, it never works that way. Not unless you heat it with a heat gun, and try and get it tacky to re-use it.
 

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There are several ways to fix this. On my old 540 I used just silcone sealant, plenty of it, and it held up for years until I sold the car. On this car, I used the window weld stuff, AND silcone sealant around the outside edges just to make sure no water would get onto my illuminated door sills, or into the car.
 

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Discussion Starter · #10 ·
I personally did not reuse the original stuff because in my eyes it will just fail again. I have every record from my car since it's in-service date, and no one has ever had that door apart. The previous owner was not a DIY guy, EVERYTHING was done att the dealership. 732 is just Industrial Loc Tite silicone that we use at work to fix just about anything that needs to be repaired in a water tight situation. IF I do ever need to get inside that door panel I will cross that bridge when I come to it. I would much rather have to deal with a PIA door repair if a regulator fails than have to worry about the original sealer failing again causing my door to leak again. I can pretty much garuantee this stuff will not leak.

Sometimes OEM isn't the best route to go.

But again, to each his own.....
 

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Can we come up with a better waterproofing solution than the vapor barrier on the inside of the door skin? Is there something we can drape on the interior of the door metal that might channel water a little better? I'm willing to put in the work here to make sure this doesn't happen.

My initial repair didn't take because I think I didn't do a complete job removing the sealant from the vapor barrier itself. With the hurricane rains yesterday, my car was a boat inside :(. Sucked out the water today, going to go at it again tomorrow, and will look to see if there is a better way to make the seal.

BTW, I got new vapor barriers simply to save myself the time and energy of removing the window weld from the old barriers. It took me 3x as long to clean them than the door metal, and I clearly didn't do a good job. Interestingly enough, the new barriers are a much lighter grey color than the nearly-black/charcoal of the originals.

So, any thoughts on making this thing more water-tight?
 

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i used the 3M window weld to do the DIY repair the first time now im starting to get leaking again... i was thinking to myself last night that there has to be better stuff then this to fix the problem... im thinking im going to go buy some RTV or silicone to repair the problem again like timmy did...
 

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I'm sure half the problem was me. I was rushing it, and probably didn't put enough care into the fix. New vapor seals will help me in the effort area, but if someone wants to come up with something to add to the fix, I'm all ears.
 

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Discussion Starter · #14 ·
Huh, maybe my silicone fix is the right way to go? THE MAIN REASON I used 732 silicone is because this stuff will stick to ANYTHING, FOREVER. We use it for just about anything at work (dog food factory) and it seems to hold in any situation. I am confident my doors will not leak again. If I do have to get inside the door for any kind of repair, I know I can just buy a new vapor barrier, if needed, and silicone it again after scraping off the old stuff. But at least I know my door won't leak. Besides, how often do you see someone's rear window regulator failing?
 

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i used new vapor barriers for the repair the first time.... i even used a heat gun to heat up the 3M window weld to soften it up and create a better seal... it worked great for awhile but then after the huricanne or tropical storm came to the east coast this weekend i noticed my carpet was wet again yesterday... i used to use 732 and a crap lot of other silicones and RTVs overhauling, repairing, and maintaining military and commercial hydraulic and fuel related systems... the stuff works great on skydrol and jet fuel (which are both extremely corrosive)... it's kinda funny i found this thread today as i was telling my girlfriend that i had to find a better solution for sealing up the rear doors last night...
 

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I am doing this in 2 weeks. Bmw dealer told me they use "Window Weld" sealant. I have the NAPA part number at work and will post it tomorrow
 

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BMW sells their own, and it's much better than the 3M I've used previously. I've got hundreds of these repairs under my belt, and not a one has ever leaked. As I said, the key is using a heat gun to activate the butyltape. Just applying the tape and setting the vapor barrier in place won't necessarilly fix the issue every time.

You're going to be hacking away at that silicone w/ a razorblade for some time when you go to cross that bridge.
 

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BMW sells their own, and it's much better than the 3M I've used previously. I've got hundreds of these repairs under my belt, and not a one has ever leaked. As I said, the key is using a heat gun to activate the butyltape. Just applying the tape and setting the vapor barrier in place won't necessarilly fix the issue every time.

You're going to be hacking away at that silicone w/ a razorblade for some time when you go to cross that bridge.
Do you have a BMW part number for the sticky stuff? If you are in NH, wanna come down and help me with my door? I could use your expertise and experience with this repair. Dinner/libations/more on me :).
 

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Discussion Starter · #20 · (Edited)
You're going to be hacking away at that silicone w/ a razorblade for some time when you go to cross that bridge.
Agreed, but at least I know FOR SURE that it will not leak again. As I stated before, how often do people need to go back into their doors for a repair OTHER than a leaky vapor barrier......

Again, to each their own, I just thought I would share MY way of fixing this issue for good, which is pretty dummy proof. No heat gun, no making sure it's perfectly set. Goop on some silicone, tape it up to cure, enjoy not having wet floorboards.

Oh, and my fix cost me nothing, I brought a bottle of 732 home from work. Not sure what the cost is at a store or if it is cheaper than a BMW part, but I would bet it is.
 
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