Greetings! I have what I assume is a unique problem, as I can't find much in the way of solutions from searching various automotive forums. I know we have some very particular car owners on here, so I figured if anybody knows the answer, they're probably on here.
My family owns several Toyotas, and I've run into this issue on several of them. Eventually, you need to get inside the door to replace a window motor, and no matter how hard I try, I can't get the vapor barrier to stay stuck. This leads to water leaking inside the cabin. Rainwater runs down a wire harness, or hits the door check, making its way to the vapor barrier. As it doesn't have a good seal, it leaks inside the car as opposed to draining down to the bottom of the door.
Toyota uses a clear poly sheet for a vapor barrier, adhered to the door with butyl rubber. When it started leaking, I figured it came unstuck as the factory plastic sheet was dirty, so I replaced it with some new poly sheet and new 3M butyl. This worked great, for a time. A year or two later, we have another leak. I figured my generic poly sheeting wasn't the right stuff. I got a new vapor barrier from the dealer, and installed that with new 3M butyl. I made sure it was firmly pressed all around with a roller, with no bubbles or wrinkles. Again, it lasted a year or two before leaking again.
The butyl stays firmly adhered to the door metal. However, over time, the poly sheet looses its ability to stick to the butyl. Factory-installed vapor barriers continue to stick indefinitely if undisturbed. I find that any barrier I've replaced only stays stuck a year or two at most. Does anybody know the trick for getting the vapor barrier plastic sheeting to remain firmly stuck to the butyl, like it is from the factory?
My family owns several Toyotas, and I've run into this issue on several of them. Eventually, you need to get inside the door to replace a window motor, and no matter how hard I try, I can't get the vapor barrier to stay stuck. This leads to water leaking inside the cabin. Rainwater runs down a wire harness, or hits the door check, making its way to the vapor barrier. As it doesn't have a good seal, it leaks inside the car as opposed to draining down to the bottom of the door.
Toyota uses a clear poly sheet for a vapor barrier, adhered to the door with butyl rubber. When it started leaking, I figured it came unstuck as the factory plastic sheet was dirty, so I replaced it with some new poly sheet and new 3M butyl. This worked great, for a time. A year or two later, we have another leak. I figured my generic poly sheeting wasn't the right stuff. I got a new vapor barrier from the dealer, and installed that with new 3M butyl. I made sure it was firmly pressed all around with a roller, with no bubbles or wrinkles. Again, it lasted a year or two before leaking again.
The butyl stays firmly adhered to the door metal. However, over time, the poly sheet looses its ability to stick to the butyl. Factory-installed vapor barriers continue to stick indefinitely if undisturbed. I find that any barrier I've replaced only stays stuck a year or two at most. Does anybody know the trick for getting the vapor barrier plastic sheeting to remain firmly stuck to the butyl, like it is from the factory?
