So I have both a 2000 civic, and a 2001 crv. I had this issue once going through the car wash (on my civic first) where a bunch of water made it past the channel that is supposed to drain the cowl near the windshield. What happens here is the foam gets old, and then the water spills past the seal into the opening where your blower motor / hvac pulls in fresh air. Honda did not design the system with a "rain hat" which would shingle and water away from this area. The other day I had this problem on my CRV - so I pulled off the cowl and replaced the foam with fresh foam. I also designed a rain-hat to snap over the opening and drive water away from this area in the event the water flow is enough to still make it past the seals (it's good to have redundant design features!) In my opinion this is how the system should have been designed from scratch.

One other thing - you need to make sure the path for water to move is clear. On my car there were some debris from the environment (tree pieces and such) Anything in the path will restrict flow and could lead to overflowing and contributing to the problem.


This is how the cowl foam looked when the part was removed. You can see it is heavily compressed and was not even touching in some spots. I took these pictures mostly for reference so I could be sure to get the new foam in the same spots. (or the correct spots)

 

Here you can see the design I made. It snaps onto the 2 tall parts of the opening. It has a surface for any water to run off so that it shingles it away from the opening. This is just in case any water makes it past the foam.

 

Is there an STL for this? Thanks!