Welding in new floor pans - JeepForum.com
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post #1 of 16 Old 09-12-2019, 10:23 AM Thread Starter
dented
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Welding in new floor pans

2001 XJ. Drivers side has a big hole. Passenger side has a small hole.

I was going to cut out the size of the pan then weld in the new metal, but I'm thinking why lose the integrity of what is still good.

Can I grind out the rust, use something like POR15 on the rest then weld the new pan on top? I'm thinking of using a plasma cutter to make holes in the pans where the jeep metal is the thickest, spot weld it and then weld the edges in. I could deal with the rest from the bottom with all metal to seal everything up.

Anyone with experience?

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post #2 of 16 Old 09-12-2019, 11:19 AM
CJ7-Tim
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1) Small to moderate size holes in the floor are not significantly detrimental to the structural integrity.

2) Hole repair or an entire floor pan replacement, you should use unibody structural adhesive instead of welding. Unless you have TIG welder you will just blow holes in everything. Remove all rust from repair areas. Rough grind the glue joint areas. Overlap any hole repairs by about 1 inch all around, and POR-15 over the repairs, the patch edges, and any bare metal.

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post #3 of 16 Old 09-12-2019, 12:19 PM
2oldjeeps
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i put in good size pans bolted to frame rails,heavy self tappers thru to good existing metal
and good body sealer to avoid voids to reduce future water leaks. i think welding causes more rust.
EVERY factory WELD spot on a new hummer in 2010 showed early rust. it weakens the metal..


btw guys on another jeep forum expressed hysteria about using self tappers! it was really fun!.

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post #4 of 16 Old 09-12-2019, 12:55 PM Thread Starter
dented
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Wow you may have just saved me a ton of work. I definitely plan to grind down rust.

I think I can weld to the unibody frame rails with MIG. 3M says you can weld through uncured adhesive. The metal is thicker there. I will definitely coat everything after.
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post #5 of 16 Old 09-12-2019, 02:51 PM Thread Starter
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I feel I need to weld the pan to the frame rail. Unibody is all structural. The self tappers would work. I think I will use a combination of adhesive (mostly) with some strategic welds. I'll take some picks.
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post #6 of 16 Old 09-12-2019, 03:25 PM
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i cot out all rust and left a one inch band where new pan fit with seam sealer.
not the least worried about the small area of floor affecting structure. it had been gone for years b4 i fixed it!!
used bolts/nuts on frame thru pan and big self threaders. pans sat in a bed of sealer
Attached Thumbnails
100_5020.jpg   100_5025.jpg   100_5028.jpg   100_5033.jpg  

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post #7 of 16 Old 09-12-2019, 06:00 PM
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post #8 of 16 Old 09-14-2019, 09:01 PM
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Quote:
Originally Posted by dented View Post
2001 XJ. Drivers side has a big hole. Passenger side has a small hole.

I was going to cut out the size of the pan then weld in the new metal, but I'm thinking why lose the integrity of what is still good.

Can I grind out the rust, use something like POR15 on the rest then weld the new pan on top? I'm thinking of using a plasma cutter to make holes in the pans where the jeep metal is the thickest, spot weld it and then weld the edges in. I could deal with the rest from the bottom with all metal to seal everything up.

Anyone with experience?

I replace and welded in new pans on my 2000 last year. Was not hard just time consuming and rust was worst than what I thought. I welded my pans in with my mig welder using .021 wire, low heat and gas.



I drilled holes on the new pans about 1/2 inch apart and plug welded them in. I used good weld thru primer along edges where i was going to weld and coated with rust bullet (same as por15 but can be painted over) then used oil base primer, good brush able seamsealer and paint on the inside. Underneath same thing. Main thing is don't cut corners and cut out all bad rust and grind away and seal the minor ones.
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post #9 of 16 Old 09-15-2019, 01:29 PM Thread Starter
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So far I've done the passenger side. I cut out all rust, ground down to bare metal in other places. I then coated the whole thing with a rust encapsulator. I fitted the pan and marked where I would use the adhesive and ground it down to bare metal again. You can weld through the adhesive when it is wet. Just remember it is very flammable so your weld will keep burning. I made holes around the metal pan and along the frame rail. I plugged welded it to hold it in place. Adhesive is stable in 4 hours and solid in 24. It is very simple, but dirty and labor intensive. I'll post some pics later.
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post #10 of 16 Old 09-15-2019, 01:35 PM
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When I installed a complete floor pan, I used uni-body adhesive, and a few self drilling sheet metal screws where the pan wanted to pull away. The prep took much longer than the repair.

.

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post #11 of 16 Old 09-15-2019, 07:19 PM Thread Starter
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I have an IronRock 3 Link. All the control arms bolt to their cross member. Bolting all that to the pseudo frame is just not strong. I cut from in the cabin and added 1/4 plate like a giant washer with nuts welded to it. It is much stronger. Next I will put in frame stiffeners. It will make it all VERY strong. The third picture is it welded back up. 4th pic is the pan cut to size. I made holes for spot welds to hold it while the adhesive hardens. 5th pic is everything buttoned up with a rust encapsulator over everything. I painted all the way to back seat.
Attached Thumbnails
Pass Cleaned out.jpg   Pass W:Plate.jpg   Pass Floor Welded.jpg   Pass Pan.jpg   Pass Done.jpg  

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post #12 of 16 Old 09-15-2019, 07:23 PM Thread Starter
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Drivers side before. And Driver's side almost done.
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post #13 of 16 Old 09-15-2019, 07:25 PM Thread Starter
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Quote:
Originally Posted by CJ7-Tim View Post
When I installed a complete floor pan, I used uni-body adhesive, and a few self drilling sheet metal screws where the pan wanted to pull away. The prep took much longer than the repair.

I'm sure some cringe at the sound of self tapping screws, but they are such a simple way to hold the pan in place while the adhesive hardens.
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post #14 of 16 Old 09-17-2019, 04:02 AM
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Originally Posted by dented View Post
I'm sure some cringe at the sound of self tapping screws, but they are such a simple way to hold the pan in place while the adhesive hardens.
I used them on an 87' Cherokee I posted here years ago. Worked well with adhesive, then if you want cut the tappers from the bottom.

I would also suggest bedlining every Cherokee floor. These things all leak water, which rusts after sitting under carpet.

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post #15 of 16 Old 09-17-2019, 10:58 AM
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you can stop the leaks, its not ez but worth it...

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