[Tech Note] - Have water in the floorboards of you BMW 3 and 5 series car? Especially in the rear seat footwell area?

This problem is very common on these cars. The problem is water is getting past the interior door vapor/water barriers. The rope type seal that secures the vapor/water barrier to the interior door surface is coming loose at the bottom and water is pouring through holes in the seal right into the car. Sometimes, you can see a trail of the water coming out of the lower light in the door panel.

The fix is to sometimes replace the vapor/water barrier and of course, the rope seal.

We have found that sometimes that repair still doesn't fix the problem! Our answer is too apply an additional rope seal at the edge of all of the lower openings in the door and add another rope seal in the original location; but to apply the vapor barrier with a heat gun to make sure we get a good bond to both surfaces. Hopefully, the good seal will force the water that comes in the door back into the door where drains have been provided by the manufacturer.

Our theory is that if the water is not allowed to get between the vapor barrier and the interior door, then there is less chance that the seals will give way in time to the constant pressure of water sitting on top of the seal that could be trapped between the two components.

This repair can cost over $200.00 per door, but it sure beats what it might cost to repair the components, wiring, and wire connectors that are located under the carpet that have gotten wet. Not including the possibility of mold growing and the carpet rotting right in the car. So, it is necessary to make sure the carpet and the floorboards under the carpet are dry. The cost for drying the carpet depends on the car and how wet it has been!