** Ultimate solution **
I have had this problem for a few years. Water leaks on the passenger side behind the glove compartmental after it rained. I have to take it to the mechanics when the fan and the electric system were damaged by the water. I was told it took them a lot of trouble to get rid of the water. However, the water problem started again soon after. It rained pretty hard yesterday and a lot of water poured in after a loud splashing sound when I first drove the car. Finally I had enough and fixed it today after reading the posts on this site. I am posting it now since I believe I found the root of the problem and the solution to eliminate the problem.
When I opened the cowl panel, the black plastic panel, between the hood and the windshield, I see a pool of water. There are big rectangle vent openings on the back wall for air intake of the fan. There are a lot of leaves and the drains were clogged solid. Water accumulated and flooded into the van via the vent openings during the night of strong rain. I cleaned the leaves and drained water and tested running the water from the windshield. Sure enough water flowed down onto the back wall and got into the car through the vent openings. I really could not believe Chrysler could have such a stupid design. Now, I not only need to build something to keep the water from flowing into the vent but also find a way to keep the leaves from clogging the drains. Why the heck did all these leaves get in here? How the heck could I keep the drains from clogging?
To make the story short, the real culprit of the problem is the missing weather strip between the windshield and the cowl panel. No water from the windshield was supposed to go down there at all say nothing about running down the firewall. Very little leave should be able to get in from the tiny holes of the screen on the panel and the drain should never been clogged. The solution is to seal the space between the windshield and the panel.
Follow the instruction in the previous posts to remove the cowl panel. It’
Clean the leaves and make sure the drains are clear. There are two plastic drain holes under the drains. You can easily pull them out and flush them with water holes if they are clogged.
I did not call the dealer to get the original part since the van is 10 years old. The weather strip from Pepboys was very chunky. I found the Windo-Weld Ribbon Sealer from 3M at Strauss. It’s very easy to use. It’s a strip of robber like chalk that can be rolled out on the windshield easily. Use a marker to help you to line it up. It works beautifully.
If you have the water problem, fix it now. It will not only get your wet and rusty but also destroy your electric system and the fan.
So check your weather strip between the windshield and the panel. If it’s missing or broken you must fix it. No leaves or water should be able to get in from there. I would use silicon if I have to. I will also make an effort to keep the leaves and pine needles off the cowl panel.
One mystery still remains. I never figured out how to get the water out of the enclosed box behind the glove compartment. That’s where the water eventually gets to before dripping out. I was told that’s where the fan and electric systems are. I really wanted to drill a hole but worried about damaging anything. Hopefully, it will dry out soon before any damage occurs.