Rust hole on firewall above wire harness

[willett]

Hey,

I'm fixing up a '73 cab for my '78 and I'm finding quite a bit of rust (no big surprise up here). Most of the holes are no brainers to fix but this one has me a bit stumped:

The hole is above the mounting spot for the wire harness on the top left corner.

How have you guys dealt with the problem?
Every time water gets into the cowel it ends up on the driver side floor pan!
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[notyo_cheez]

My donor cab had minor rust out along the cowl seam on the firewall, the seam sealer shrank over the years and pine needles decayed inside the gap. I just used some fiberglass filler and covered it up.

[legendman]

I had the same problem on my 82 K30, any water in the cowl area where the wiper trans is would run to the l/s and there was a hole rusted through there.
I made up a piece from some sheetmetal and welded it in then sealed it up with some seam sealer. Checked after a couple days after the sealer died and ran a bunch of water in that area and no more leak.

[willett]

I was thinking about spraying rhino liner or undercoat or something similar in there once she's all Sean sealed and patched up. What do you guys think?
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[snm95ls]

I'd think that a good epoxy primer and urethane seam sealer ought to do the trick quite well.

I guess a bed liner type of material could work, but I wouldn't want the texture in there as I would think that it would tend to hold water and debris.