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View Full Version : Advice Wanted - Rusted out floorboard


lawsoncl
October 7th, 2017, 15:53
1989 MJ. I finally got around to pulling out the carpet. I was expecting a little rust, not holes on the drivers side. Turned out those brown stains on the carpet were not from my boots. :{

Looking for advice on the repair from sopmeon who's gone through this. I'm thinking trim up the rusty holes, cut and bend some sheet metal to cover the area from the inside (maybe outside too?), and use either epoxy or a polyurethane adhesive to attach and seal it up. I have a MIG welder, but think I'd just end up blowing holes in the sheet metal. After that, wirebrush anything else, paint with rust converter then bedliner everything. Sound like a plan?

Drivers Side Inside
http://i64.tinypic.com/2qmnad1.jpg

Drivers Side Underneath
http://i66.tinypic.com/29c86ty.jpg

Passenger Side Inside
http://i68.tinypic.com/oh4oqr.jpg

Passenger Side Underneath
http://i63.tinypic.com/29qe3c1.jpg (http://tinypic.com/r/29qe3c1/9)



-Chris

RCP Phx
October 7th, 2017, 18:01
It's really not to bad, I've dealt with worse. You need to clean all the rust off FIRST so you can see what your dealing with. I would weld it up, but that depends on your welder and welding skills? Do you have a air compressor because you can get a sheetmetal flange tool cheap at HF!

lawsoncl
October 7th, 2017, 23:24
It's really not to bad, I've dealt with worse. You need to clean all the rust off FIRST so you can see what your dealing with. I would weld it up, but that depends on your welder and welding skills? Do you have a air compressor because you can get a sheetmetal flange tool cheap at HF!


Might have to practice a bit on sheetmetal. Most of my welding has been thicker stuff. I might pickup an air nibbler too at HF. Worth buying the pre-formed floor pans at $50 each?

8Mud
October 8th, 2017, 00:09
It's really not to bad, I've dealt with worse. You need to clean all the rust off FIRST so you can see what your dealing with. I would weld it up, but that depends on your welder and welding skills? Do you have a air compressor because you can get a sheetmetal flange tool cheap at HF!

Like the man said; first you have to see what you have, surface rust is no factor, rot is. The only way to know for sure is to clean it down to bare metal and over larger area than you think

A flat coarse wire wheel on a angle grinder is the fastest way to clean it down to bare metal, over and under. A drill with small round wire brush for the corners and tight places. Full face protection is recommended, at the very least eye protection, if a bristle comes off the wire brush, it is traveling fast enough to bury it to the bone. I had to pull one out of my cheek with pliers and had to pull hard to get it out.

What I did is to cut a piece of sheet metal with some decent overlap. Paint it with Hammerite flat black on the down side, leave a little bare metal away from the edges of your patch so you don't foul your tip. Spot weld/tack one edge. gently hammer your patch flat as you weld, with a ball peen hammer. The heat from the weld helps the sheet metal to form. When your done with the top gently hammer the rough edges underneath flat, paint will likely ooze out some. Paint underneath with Hammerite flat black. Flat Black dries quickly, very quickly if you put a work lamp pointing at it. When the flat is dry, cover with black gloss Hammerite. Let the gloss dry, it will take a lot longer. Cover the bottom with undercoat, butyl undercoat is good enough. The deal is, sometime or other you may want to strip a section back off, butyl undercoating is a compromise, it sticks well but not so well it is pain to strip off if you have to. My way may not look factory when finished but it lasts. It doesn't have to look pretty, it has to last.

The best way to weld it is with a series of spot welds or tacks. About three seconds a tack. Every few tacks hit it with a wire brush. Clean out your MIG tip when needed, use tip spray. It is slow going, but seriously, by the time you have to deal with the burn throughs, it actually saves time over trying to run a bead.

I've tried just fixing the bad spot, every year new bad spots would show up. If you fix the rot and paint it correctly it will last for many years.

The trouble with doing the whole pan is in all likelihood you have a bunch of unnecessary extra welding to do.

The Renix is actually easier to do, the floor pans are thicker metal, fewer burn throughs.

This way works for me, there may be other better materials available, but I tend to stick with what I know works. Try to cut too many corners and you may be doing it again in less than a year, right next to last years repair

Ralph77
October 8th, 2017, 00:54
I have seen worse myself. Depending on how bad the metal is around the actually holes maybe you can get by with a patch job. Back in the day when I use to run CJ's we would just rivet sheet metal in after cutting out all the bad metal. Of course a CJ has a frame so it was not like the floor pans were as structurally important.

Tim_MN
October 8th, 2017, 07:25
Buy some floor pan patch panels, and use UniBody panel adhesive. UniBody panel adhesive is used on newer vehicles and testing shows greater shear strength than spot welding. If you do weld, simply follow the original spot welds where the metal is thicker and/or double thickness, then seal with auto body seam sealer.

I removed a rusty XJ floor pan and used a patch panel and UniBody panel adhesive, the results were excellent. BTW I work at an Aerospace TIG welding shop.

lawsoncl
October 8th, 2017, 12:19
Buy some floor pan patch panels, and use UniBody panel adhesive.


Yeah, time to start cutting back until I get to solid metal. I think the passenger side might be fine with some wire brushing and repainting. Got a few other projects to get done this weekend first.

I'm considering ordering the preformed pan for $50 just to save time. Then trim cut it down to about 3/4" bigger than the hole in the floor after I cut out all the rot and get back to solid metal. I've got a friend who does body work who swears by the panel bond stuff.

lawsoncl
October 9th, 2017, 13:51
Drivers side after a bit of wire brushing and grinder. Switched to a pair of pliers after realizing the fuel lines are right there. Time to go get that air nibbler. Passenger side isn't nearly as bad. About a 4x6 area that's weak with a few small holes starting. Probably cutout the section between the frame rail and side and replace it though.

http://i65.tinypic.com/s2ab20.jpg http://i67.tinypic.com/2lka54x.jpg

lawsoncl
October 9th, 2017, 14:00
Anybody use these? Seems like time saver to trying to bend up my own pieces, especially along the tunnel. Looks like you get two pieces per side as the MJ has a frame rail in the middle that the XJ does not.

https://www.andysautosport.com/floor_pans/jeep_comanche.html

Tim_MN
October 9th, 2017, 16:51
Bending you own is mostly a waste of time. C2C and Sherman are thicker metal and are formed better than the cheaper stuff. Cheap parts are cheap for a reason.

ehall
October 9th, 2017, 18:01
My advice, cut it out, cut some metal to fit (or buy patch panels if you can), tack around the edges so it doesn't move, then lay beads of automotive seam sealer around the inside and outside edges. I did that with some holes in the floorpan a few years ago and it hasn't gone sour at all

http://www.eric-a-hall.com/gallery/albums/Floorpan/Front_Driver_Cut.sized.jpg

http://www.eric-a-hall.com/gallery/albums/Floorpan/Front_Driver_Tacks.sized.jpg

http://www.eric-a-hall.com/gallery/albums/Floorpan/Front_Passenger_Seam_Sealer_Outside.sized.jpg

lawsoncl
October 9th, 2017, 19:36
Anybody use these? Seems like time saver to trying to bend up my own pieces, especially along the tunnel. Looks like you get two pieces per side as the MJ has a frame rail in the middle that the XJ does not.

https://www.andysautosport.com/floor_pans/jeep_comanche.html


I'm confused. I was wrong about two pieces. The picture is both drivers and passenger sides. Looks like I'd have to cut it down the middle to get two pieces on either side of the top channel - which apparently the XJ doesn't have. Or cut out and temporarily remove the channel. Not the drop it in, tack weld and go I was thinking. Still going to order the pans though.

lawsoncl
October 14th, 2017, 19:29
Okay, got the patches welded in. I opted not to buy the preformed panels because the Comanche has that extra to channel running through the foot well so I'd have to cut them up anyway. I found some nice 18 gauge metal to use, and it really wasn't that hard to shape, then beat in place with a mallet as I stitch welded it in. My new favorite toy is the air nibbler, btw. Wow that thing is really nice for cutting sheet metal. Probably going to return the flanger though, as I didn't use it.

I sprayed any remaining surface rust with rust converter and will grab some seam filler tomorrow. I have some grey tractor primer I used on the body (which I still haven't painted because I like the grey color) and some gloss black tractor paint with hardener.

I'd rather not put carpet back in. What I took out was kinda nasty looking anyway. Thinking about roll-in herculiner. Too cheap to go get real line-x or similar.

Of course now that the seats are out, time to consider a seat swap.

I also noticed a few leaks - rear diff pinion seal, xfer case output, and back of the engine. It never ends right?