Water leaking from somewhere - floors soaked in back seat!

What is causing the floors in the back seat of my 2002 BMW 525i to get soaking wet whenever there is a lot of rain? At first, only the floor behind the driver’s seat was getting soaked. Now the floor behind the front passenger seat is also getting soaked, altho’ it’s not as bad. Behind the driver’s seat, the carpet right up to the “rail” (on which the closed door sits) is sopping wet. Mechanic detected a “plug” on bottom of car that was rotted out. Replacing it did NOT fix the problem - in fact it’s worse! I went to topix.com and it seems a LOT of Beemer owners have had this problem - which seems pathetic for such an expensive fancy-schmancy car. I had 2 Toyotas previously - for 10 yrs and 13 yrs respectively. The one I had for 13 yrs had a moon room (as does my beemer) - but the Toyota never had this problem.

I would be grateful for insights!

Well, if there’s a moon roof on your vehicle, check the water drains for the moon roof for blockage.


I will tell that to the mechanic (can’t check it myself). I had asked initially whether it could be coming from moon roof - and he said there would be water marks on the inside ceiling or on “walls” of the car - but I will tell him about this reply.
Someone else said it could be “vapor lock” problem inside the doors.
Have you heard of that problem with this symptom?

Take a look at the door glass… See that rubber wiper between the glass and the edge of the door? If water can get past that seal and into to doors, and the drains in the doors are plugged up, the doors fill with water until it runs out from behind the interior trim panels and into the car…Open the doors, get on your back and look up at the bottom edge for the drain holes…Make sure they are clear…Next, remove the back seat…See what you discover under there…

Thanks. I will check that out (or have my mechanic check it - no way I could remove back seat).

BMW seats are far easier to remove than most. You don’t want to remove the seat back, just the cushion. Just push back slightly on the front edge of the cushion about 6" in from the door. Sometimes I do it with my thigh with my knee on the floor, but yours is wet. At the same time, pull up on the front lip of the seat. Repeat for the other side. Once the front edge is popped up, pull forward so that the rear edge is clear of the seat’s back. Lift.