I have a 2003 BMW 525i. A couple of years ago, after a heavy rainstorm, I found water in the footwell of the backseat behind the driver’s seat. I took my car to a mechanic and he mentioned the door’s vapor barrier and the vapor barrier was resealed. Again a heavy rain storm, back to the mechanic and the vapor barrier was resealed. This has happened three times and I feel that there is a problem somewhere that has been overlooked by my mechanic. I hope that you have a suggestion that will solve this problem for me. Normally, my car is garaged, but when out of town, my poor car is at the mercy of the weather. My car needs help.
Do you have a sun roof? If so have it checked out for blocked drains (s).
Good place to look first…water comes down the front windshield supports.