1) I had just finished washing the car, but did not see any sign that water had entered through the door seal.

2) The car had been driven in the rain recently, but I didn't see any signs that water was entering through the floor board.

3) The floor of the front passenger side is dry.

4) The water appeared to have been there for a while. There is a piece of padded rubber under there that had disintegrated to an extent. The same piece on the driver's side is fine.

I have only had the car for about 3 weeks. I will be checking with the previous owner to see if he was aware of any leak back there. However, he cared for the car meticulously and I'm sure would have taken care of this problem if he knew it existed.

Are there any known areas where water can enter back there?

Thanks.

Sean
'88 M5
'76 2002