remove the carpet on the r/f under the dash.check for water on the carpet backing leaking through the firewall.then it rolls back to the rear floor board.

Answered by cadieman (expert)
2,849 answers provided

The same thing is happening to my S80 2002. The water is under the mat on the drivers side and pooling behind on floor of passenger side. There are no leaks in windshield or sunroof had it checked by glass expert. I can actually hear water swishing around when I stop the car.

Answered by nac
0 questions asked

you gotta bad leak from the firewall.open the hood and check all the r/side rubber gromets one maybe fell out or is lose.also youll need to check the seams in the r/f area they are sealed with seam sealer.but sometimes the seam will open up.then pull the r/f carpet away so you can see the metal floor
board.lay a hose on the roof so it will run down the windshield on the r/side.then go inside and watch the floor board for water coming in.im thinking its a seam because multiable cars have the same problem.

Answered by cadieman (expert)
2,849 answers provided