Good morning. I have a 2004 XC 90 and had this same problem. You have clogged sunroom drains on your vehicle, which I was able to repair on ours very easily.

You will need to remove the grab handles near the windshield and the plastic cover for the pillar. You will see the clear plastic drain tubes running down the pillar into an L-shaped rubber fitting at the bottom. Pull the tube from the rubber fitting and pull the fitting out and you will find it clogged with all sorts of dirt and organic matter. Clean it out really well and re-install it and you will have no further problems.

You probably will want to pull the front seats out to remove the carpet so the padding on the back of it will dry, or you will have a bad mold and mildew problem.

Good luck!!

I jut fixed this last weekend on my wife's car. There are four drain holes on the sunroof- one from each corner. The front left and right drains run down the front left and right columns and into a rubber fitting that carries the water into the front quarter panels to drain. When the rubber fitting gets clogged with gunk the water backs up into the passenger compartment and floods the floor mat. The fix is easy- under the grab handle are two bolts that hold the plastic column cover on- unscrew the bolts, firmly pull the plastic piece off and expose the drain tube. pull the tube out of the rubber fitting, pull the fitting and clean. you can also run a wire down the tube from the sunroof- but be careful it is does not puncture the tubing. This should solve your problem. To test pour water into the sunroof drain and verify it flow freely out from under the four quarter pane(s.

Check the front drains in the sunroof. Check the drains in the engine compartment that are under the windshield, leaves can clog things up pretty good.

Klaus
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The more I learn, the more I forget. So why learn?