Rusted floor board - need advice.....

Man, I pulled up the passenger side carpet to anchor down my new cage and discovered some pretty nasty rot - chunks of floor stuck to the padding and now I'm looking right at the end of my muffler through the floor.....

Cause:
I believe that the primary cause of this is due to the previous owner having lived in the mountains and parking it under a pine tree - I'm thinking that the cowl is clogged with debris because I've had the Jeep in the garage for weeks and the carpet padding is soaked. I've always noted a musty smell inside the jeep after a rain. No, nothing wrong with the heater core. I know that the windshield channel is fine - had the glass replaced a while back and specifically looked for rot there.

Cure:
First, how would you guys go about clearing out the cowl? Drano? Enzymes? Hooked coat hanger to get the big stuff?

Second, how would you guys go about having to replace the entire floor board from the front foot well, back to just behind the front seat rear bolt crossmember? The seat bolt crossmembers are rusted at the spot weld flanges, but solid otherwise. I was thinking of cutting the floor out, trying to leave the bolt crossmembers in place, then go to the salvage yard, find a non-rusted donor and sawsall out the new floor, and weld that in place?Better ideas?

Third, what product should I use to treat the repair to stop future rot? POR 15? Undercoating with a paint base? What can I use to treat minor rust areas to prevent further rot?

TIA!

I can answer your third question. www.eastwood.com
Rust Encapsolation-stops rust and coats the surface
Seam Sealer-coat all seams on both sides and around the back seat crossmember
Rubberized Undercoating-Could be used for the underside after it's treated with Rust Encap.
Or use some type of roll on bed liner.
I was lucky that my floor was just surface rust, with one small hole at the pass side foot well. An a small leak at the seam by the kick panel on the pass side. I cut the hole out, welded in a new piece of 2"x2" metal plate, 1/8". Coated it with the RE, Seam sealed everything, sanded the floors down and coated them with RE. Used the Rubber undercoating to add some sound damping to it. Layed down 1/2" of carpet padding on both sides and around the trans tunnel. Problem solved. I did use the Rubb under coating for the underside as well as brush on bed liner. POR15 will work as well. But my father has a business account with Eastwood so the discount was well worth it. juice

this place has enouch xj body parts to almost build a new one from scratch. I ve been thinking about doing my floor.
http://www.chryslerpartsdirect.com/moparonline.htm

Floor pan - 4 door station wagon 84-93 $200.00 $160.00

Is that all ya' need..? I might do it just for fun..!!

I had the same problem w/ my cherokee. Just discovered it last night. But only surface rust and 2 small holes. As for mine I'm sanding it down, scuffing up the floor, vacuum, degreaser, then walmart rust converter from spray can, fiberglass the 2 small holes, duplicoler truck bed coating (roll on) 5-6 coats, undercoat just in case, done. The most annoying part is my jeep has no rust on it in the back, driver side, but then the passanger side is another story. It just leaks water all the time out of the AC unit. Is there a fix this? My fix is the layers of truck bed coating and removing the diaper like material under the carpet so even if it's wet it will dry fast and the rubber coating will not rust and just dry off in time.

POR-15 is tough stuff. Having done body work for over 30 years, I would degrease it, knock the loose stuff off, and POR-15 everything from both sides. If strength isn't a big consideration such as in seat anchors, I would take some duct tape and cover the holes from the bottom after the POR-15 cures and then get some fiberglass resin and mat. Coat the floor from the top and lay the mat in. It will seal everything from the top and make it so you're not doing the Fred Flinstone bit. Then remove the duct tape and hit the bottom side with a good shot of undercoat. It will last at least 10 more years if you do it right and its a quick cheap fix.

Bring it to Ouray and we can do a demonstration for everybody.

Thanks for that link chadc , will definitely put that to good use!

Replaced a small section of my floor on the passenger side too and it rotted into the same area of the frame rail where the two pieces are spot welded. The floor pan itself was just sheet steel and then I cut the frame rails down into good metal, welded in a new section, wrapped it and called it done. That Eastwood Rust Encapsulator is really good stuff, pretty much the same as POR-15 but it dries kinda dull finish. Doesn't need to be topcoated either and prep is minimal. Good luck!