wet carpet!

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It's been raining quite heavily here for the past couple of days. Today, upon returning to my truck which was parked at the local train station, I noticed a nice little puddle of water on top of the carpet on the passenger side. After going ballistic for a few minutes, I began investigating the source of the cursed wetness. What I could see was a nice little trail of water coming down in back of the seat on the rear wall of the cab. It appeared to originate from the rear window seal somewhere. Now, when I got home I removed the kickplate and the piece of molding so I could pull up the carpet and check things out. After pulling up the carpet, it looked like most of the water was coming from the rear window and trickled down the channel inside the door frame and made its way up to the front. The truck was parked facing downhill so I suppose this could explain the puddle only up front. I also noticed a couple of drips coming from around the heater duct, where the inside max ac air intake is. Where the floorboards start to turn up towards the firewall there was no water at all and no sign of any leaks. I'm really dreading the possibility that I may have cowl cracks . I had a similar water leakage problem on my '88 W100. It turned out to be a combination of the rear window seal, door seal and cab clearance lights. Has anyone had this kind of leak? What are the signs of leakage due to cowl cracks? Any info would be greatly appreciated. (I've already done a search for "cowl cracks" and read all of the results. But there was little discussion of the leaking, except for the windshield seal, which I'm going to go look at right now)

Frustrated,
SP