I've had this problem for some time. I have had the panel that sits between the windshield and the hood off three times trying to figure out how water gets from that cavity under the panel to a location somewhere behind the dash, after which it of course flows down onto the cab's rug.

I did at one time use silicone caulking on every seam that I could see in that gully apparently to no avail. I've been thinking about spraying a couple cans of the spray sealer we all see advertised on TV... the one that the guy puts a screen door on the bottom of a rowboat, sprays it with that stuff, then demonstrates how the boat floats........

Every rain, I have a wet rug. I started putting the truck under the carport alongside my late wife's car to have it dry out thoroughly and stay that way.
However, today I hand washed the truck, not using excessive water, but once again I have a wet rug. The water can get on both sides of the cab but it is heaviest on the passengers side.

I thought perhaps the water was somehow draining past the windshield but there is no seam there and the glass is sealed thoroughly. I bought the truck new and of course it didn't leak then. What am I overlooking? (Joe)

 

Did you actually pull the windshield trim off and check/reseal around the windshield? I had the same issue with my 1988 Ranger. The passenger side carpet would always get wet. After checking all that I could, I pulled the trim off and found that it was actually leaking from the middle of the top windshield. The water would then run over to the passenger pillar and then down to the floor behind the dash. I found it by removing the inner trim and pulling the carpet back, then using a garden hose and slowly running water around the windshield until I saw the water running down to the floor.

 

Common Sense: Yes, I did have all of the windshield molding off and did seal all around it. However I may have missed a crucial spot. Of course I didn't actually remove the windshield but it appears to me that it simply sits in a recess of sorts with no actual cuts, seams, access of any kind to the cab.

I've had the rug up in the past in order to dry it out which would have been a good time to do the water hose procedure... never occured to me for some reason. When I have the time where I can give this problem my undivided attention, that's exactly what I'll do, after which, I'll get back with an update. (Joe)

 

I also found it best to have somebody helping by watching for the water to come in. That way you'll know where you were flowing the water when it started coming in. I was going real slow around the windshield when I got to the middle and heard a "I've got water" from my son. Have you siliconed up all of the POP-OUT floor plugs? I had one in our 94 Sable that would no longer seal tight that allowed water to enter making the rear drivers side carpet soacked. Also any firewall penetrations. Just trying to help cover all possibilities.

 

I am agree with the solution provided by "Use Common Sense" because I also face such problem. Actually I pull the windshield trim off for some purpose and while putting back I left a spot in seal which cause leaking due to which driver side carpet was gone wet. So the suggestion is to recheck the seal and you must flow water on the windshield from all angels to check either it is leaking or not.