Noticed that there was some wetness on the passenger side carpet after a recent rain storm. I was able to see the wetness concentrated near the black plastic foot well and thought that was the only area that was wet. I then did an internet search on wet carpet on passenger side Chevy Express van. Found out that this is a fairly common issue with these vans as there is a drain underneath the black cowling in front of the windshield that gets clogged with leaves and other debris.
I took off the passenger side windshield wiper and then removed the small black screws that attach the cowling to the body - this allowed me to move the cowling enough to get a look in there:
On the above picture, on the left side where you see the most "white" underneath there there is a rectangular drain hole that has a hose attached that drops down behind the coolant reservoir and exits out the bottom to the ground. This is the drain for the area under the cowling which needs to be open and clear for the water to exit that area. When I took a flashlight and looked in there it looked like someone had dumped their used coffee grounds in there. There was approximately 2 cups of that stuff in there and the drain was completely clogged - there was a lake in there.
I then took a 36 inch long cable tie and stuck it down the drain hose behind the rectangular hole - which was filled with water - and moved it back and forth until there was some opening in the hose which allowed the water to begin streaming out - not gushing mind you like it should have been. I then took a hose and put some water in there and kept moving the cable tie until it did finally gush out. Then I put more water in there to clean it all out. That was done - good news there.
Now I removed the plastic kick panel and the black foot well cover and started lifting the carpet expecting to find a little bit of moisture under there. What I found was a lake under there. Because the carpet has a rubber backing it did not appear to be wet, however it was very wet. Here are two pictures with the carpet lifted and removed:
On the picture directly to the right of the engine cover there is a black curved piece of plastic. That is where the water comes into the passenger side of the floor when the cowl area is flooded. I used towels to dry up as much of the fllor as I could in the picture, however I found out that the entire floor was wet - both driver and passenger side. The entire carpet needs to be taken out and dried and the floor needs to be dried out. If I had not found this I am certain that the floor would have rusted out and there would have been serious mold growth in my van. Not good things to have to deal with.
Bottomline - Probably a good idea to take some time and check the cowl area and confirm that the drain hose is functioning because you can have a wet floor and not even be aware of it.