Windshield leak is likely. Does the car have a sunroof?

I found the same thing on my 1987 740. I checked for leaks and found
none, so I took a razor knife and cut the flooring out, very neatly in
that foot area. The water was through the carpet, padding and to the
metal. It would never have dried like that.

First things first, get carpet (if you have it) off the floor and dry
it.  From there, with the carpet still peeled away - get in the car
under a soaker hose and look for leaks.

jamie

Several  possibilities, but first things first.

1.  First remove any floor mats and use cloth towels pressed hard into
the carpet to get as much moisture up as possble.

2.  Check the cowl drains to be sure they are unplugged and can handle
a lot of water..

3.  Did  you have the front windshield replaced recently?  If so they
might not have gotten it seated properly.

4.  If the car has a sunroof is there any evidence that the water
came  down from the seiling?

My 245 has a leak at the left rearest sidewindow. We have had it taken out
and remounted with a new rubber seal, without any result :-(
It is still leaking. I think we have to take it out again and remount it
with some grease and see if that helps.