There have been several people who have posted in the forums complaining about wet floorboards. This isn’t the same problems owners can encounter when the heater core goes bad, and starts leaking coolant. These forum members are experiencing clear water on the floor, not coolant.
This problem is generally caused by (2) problems:
1) Moisture and dirt can collect at the front of the drip rail and either cause rust, or get in behind the seam sealer. When it gets in behind the seam sealer, or leak through the rust, it runs down the windshield pillar and down the firewall to the floor.
The photo above is an extreme example of rust along the drip rails, but an example of what can happen.
2) The drip rail causes rain water to run down the side of the windshield and in to the cowl. The Moisture and dirt can collect and cause the cowl to rust. Once a hole rusts through, the water can run down to the floorboard.
In the photo above, you can see where he cut a section from a donor vehicle and welded it in.
If you have a leak, first check the drip rail for either a rust hole, or cracks/gaps in or around the sealant, and seal as needed with silicone or seam sealer.
If the leak isn’t there, pull the windshield trim and look for rust. If it’s minor, you may be able to clean and seal it up.
If the leak isn’t there, you’re going to have to pull the dash.
All the photos on this page were contributed by Zman.