I have a 1998 Dodge Dakota in very good shape. I bought it from my brother who has owned it since 2000. I drove the truck from Reno, NV to southeast Alaska where I live, and all along the pacific coast. It rained a LOT and I noticed pooling of water on the floor at my feet, soaking the carpet completely and pooling up. I thought I was tracking water in the truck from my boots. BUt I have had it here in Alaska for 7 months now, and it is still HORRIBLE! It rains here all the time and I can’t get rid of the puddles. There are no plugs in the floor for drainage and I can’t figure out where it is coming in. The windshield looks good, and the door seals look good also. I cannot figure out where the water is getting in so I can stop it. THe truck is going to rot and rust if I can’t fix it! And here’s the thing, the water is pooling on BOTH sides of the floor-passenger and driver. I am baffled. No one ever sits on the passenger side so its not coming from boots! there is no way for water to flow from one side of the floor to the other.
Here are some possibilities. A previous owner may have run something through the firewall such as wiring for a stereo upgrade or added meters (particularly oil pressure).
The drains at each corner of the cowling are plugged up. Open the hood and look in the corners closest to the windshield. There should be openings that run down inside the fender, just forward of the doors. Sometimes these get plugged up with leaves.
Do you have a sunroof? It has drains that could get plugged up.
Open the doors and look for the door drains. There are cutouts at the bottom of the door cavity. Make sure they are clear. They can get plugged up, especially if someone had some aftermarket “rust proofing” done. That would also affect the floorboards in the back seats.
The windshield may not be as good as you think.
My 2000 Blazer had a leak in the seam between the inner fender and the firewall. I found the leak by running water into the windshield cowl and using a flashlight under the dash. The light reflects off any water leaking into the interior.