If it were yours, what would you do (floor pans)

[Billy Darson]

Fond Hello to you all.

 

I'm a new member but long time lurker of the CC Forum, 

Recently I've jumped into eliminating water intrusion and cleaning up the rusty and Swiss cheesed floor pans to asses what would be the best approach to handle it.

I have a POR 15 floorpan/trunk repair kit(essentially, had to buy separate items to compile the kit that whey were sold out of). Which typically comes with some fiberglass mat to lay, and wet out, with the POR15 over the questionable rusty metal. So where I'm at is, should I remove the side supports and the center channel frame rail cover? from the bottom the frame rails look fantastic, like the undercoat really did its job at protecting the metal. Which I will have to reapply, any suggestions on undercoats? the interior, well we know... LOL. While lurking and searching posts on the topic of floor pan replacement, I saw many people suggested the floor pan replacements offered by KeyParts if you had the $, or if you're handy with welder, make em.

Well, I'm ok with welding, not terrible, but far from good, safe to say i'm a novice. So regardless which method I choose it looks like I'll be welding. at the very least welding the side supports back on and center channel/rail cover...

 

So if were your MJ and you had this kind of rust damage, What route would you take for a proper long-lasting  peace of mind repair?  

 

Much thanks for your input.

[garyweb3]

I had new panels installed on my 87 Comanche and I think they were worse than yours.

[89 MJ]

I’d remove the supports, weld in new keyparts floor pans, then put the supports back in, after they were sandblasted and primed with a weld through primer. 

[Boilermaker]

If you're planning on doing some welding anyway and the parts aren't cost prohibitive, I suggest using the Key Parts floor pans and supports. The Key Parts panels i've used have been good and the time saved over piecing together patches can be spent on other fixes. There is likely more rust you can't see under the floor supports and factory seam sealer. You'll be able to get at more potential problem areas with the floors removed.

 

The welding doesn't have to be visually perfect since it should eventually be covered in seam sealer anyway (plus any sound deadening, carpet, etc.)

 

Good luck with the repairs and welcome to the forum.

[eaglescout526]

I used a dryer for it’s sheet metal to create a new floor pan in my XJ. Little bit thicker and already coated in anti rust stuff. But that’s just my broke self. 

[Billy Darson]

Got after it a bit more, finding and exposing where the rust line meets clean bare metal.

 

Appreciate the feedback Y'all!  I had a feeling full on replacement would be the way to go. Guess I needed the outside confirmation to give myself permission to go whole hog.

 

Jegs wants nearly 200 for 1 side and 125 for the other? EEks. I'm no metal worker, LOL. so with that said modding a Cherokee floor pan set seems like a lit of a bother, and I'm definitely not confident enough with my metal skill to attempt the dryer patch-@ Eaglescout. I appreciate you're resourcefulness! Need to hone my metal skills to be as resourceful. Save that money.  those with the skills, do what those without the skills, pay out the boot hole for. Hats off to you sir.

 

 I tried searching summit, no dice on the MJ panels. Jegs appears to be the only ones with them in stock. KeyParts doesn't sell directly?? am I mistaken on that??

I've been burnt on Ebay before, so id much prefer to go with a credible source than deal with that mess again. looking for a middle ground Between getting scammed and bent over a barrel.  Any suggestions there?

 

All of the supports look like they're seen better days 89 MJ. some eaten through metal on the drivers side center support. and all of them seemed to dent fairly easy when I was chiseling off the flake rust. But I suppose I won't know if the supports can be saved until I get them off. chances are though they'll need to get replaced. no telling how much Ill mangle them getting em off. Ill probably use my rotohammer in hammer function with a chisel tip and a prybar to get it all out. I don't have an air hammer, but figure its similarly effective... time will tell eh?

From the other people that have put in the new floor pans, what did you do about the seat studs? I have a feeling I should make a template of where things are before I go hacking and a prying.  

 

I feel like I've learned the broad strokes of the process from the community members that did us all a service by documenting their work in doing their floor pan(and other) repairs. for that, I salute you.

One of those gems that stuck was the weld through primer. shout out@ 89MJ. 

 

Anyone use Jegs seam sealer? I'm sort of stumbling through the dark here on this project. First time doing any project like this, usually stick to stuff that can be fixed with wrenches, grease, and duct tape. so yeah :)  

 

Thanks again!

Edited September 29 by Billy Darson
incomplete sentences

[Billy Darson]

1 hour ago, Boilermaker said:

If you're planning on doing some welding anyway and the parts aren't cost prohibitive, I suggest using the Key Parts floor pans and supports. The Key Parts panels i've used have been good and the time saved over piecing together patches can be spent on other fixes. There is likely more rust you can't see under the floor supports and factory seam sealer. You'll be able to get at more potential problem areas with the floors removed.

 

The welding doesn't have to be visually perfect since it should eventually be covered in seam sealer anyway (plus any sound deadening, carpet, etc.)

 

Good luck with the repairs and welcome to the forum.

Thanks Boilermaker.

you've voice what I have felt I needed to do. the more I can get at the better off Ill be later down the line.

[ThatJeepGuy]

Any approach/attempt to fix your floors that involves removing your unibody cap and also this side inner rocker cap is a better approach than Not.

 

I find it best to drill out all of the rosette welds and then pluck these 2 pieces out before I start making the decision on a full floor pan or repairing only sections.

 

The barbarians that simply plop the small cutouts of new floor On Top of these unibody caps are soo sadly mistaken of how they in fact did NOT fix their floor pans and more soo they just invited bigger problems later on once that original in-between layer rusts away, then turning the unibody into a debris and rust receptical.

 

Because the MJ specific floor pans are a rather recent offering, also based on my experience with the KeyPars XJ specific floor pans and their fitment - i would pony my bucks over for nothing other than the KeyParts MJ specific pans. The simplicity and ease of final fit and finish is worth the $$ in my opinion. Even if it comes down to an ebay purchase - thats what a credit card is for. Any issues or hangups and you let the CC company fight thrm to get their money back - not you fighting for yours.

Any of those pages portraying the XJ and MJ as universal or same fitting is wrong. The cheapy C2C generic pans are fine for something youd want to spruce up and re-sell quickly all-be it thats what the old appliance metal is for 😜. But if you plan on keeping this jeep a long time, do it right-er once.

[ratrapp]

definitly get the mj specific pans.i used the xj pans because at the time keyparts hadnt made the mj pans yet.there is alot of cutting hammering and cussing involved using the xj style.i ordered off of keyparts ebay store and didnt have any problems.

[Boilermaker]

My floors were in decent shape so I only had my floor supports replaced. The shop that did it drilled out all the spot welds to remove the supports. The OEM supports probably could have been reused. He cleaned up any surface rust under the supports and where the factory seam sealer was prior its removal. Then put down a layer of 2k epoxy primer, 3M 2k seam sealer in the factory locations and another coat or two of 2k epoxy primer.

 

It's a lot of steps, but since I don't have any welding skills it's something I didn't want to have to address again.

[Billy Darson]

I went and bought all new supports and drivers and passengers floorpans from Keyparts Via JEGS. glad I had a tiny wad-o-cash put aside for such an occasion.

Found some sexy high temp paint and some rattle can undercoating while I was getting fresh wire wheels and flap wheels from the local Tractor Supply Co. I couldn't resist the high temp paint, oooweee! LOL. 

I will commence the project when the parts arrive. Need to source me some weld through primer though.

 

@BoilermakerI'm not hip to the 2k. I've heard it mentioned on a few Tube channels, but overall ignorant about its benefits. I've got some more learnin' to do.

  

@ThatJeepGuy   I figure while I'm going this deep, might as well dig a bit deeper, get at as much as I possibly can.

 

@ratrapp Glad you got the XJ pans to work for you. I'm pretty sure Id be doing the same if Key parts hadn't made the MJ pans.

probably an extra helping of cussing, just to reassure the neighbors I'm having a good time elbow greasing the pans to fit.

 

 

thanks all for the support and suggestions   

[Billy Darson]

So I went ahead and removed the topside corner supports and the topside rail supports. casualties of the process as I had imagined. I had to slice out the corner supports with an angle grinder with cutoff blade, even after drilling out the welds and trying to hammer and chisel bar them loose. had to do similar thing to the topside rail supports so that I could fit my tools to get the sucker loose. 

Ground down the booger welds and wired off a boat load of the goobers of seam sealer. I probably have more to remove but for now its much improved. gave the interior a spray down with a fairly concentrated soap water mix to  help get the rust dust and seam sealer dust off the surfaces, and let the frame rails get a good soapy soak. I took a soft bristle brush to the frame rails and scrubbed em as clean as I could and gave a rinse. Did this process twice. 

 

Here's where I'm at now.

I fit the new pans, traced them. Removed the worst of the metal, exposed frame internals. did a bit of clean up cutting, but as you can see from the photos, i was pretty conservative about how much I was cutting out. Figured more metal= more strong. but maybe more issues in future?

 

So how far would you go on removing the old material knowing that full length pans are going in?  

 

Edited November 6 by Billy Darson
typo correction.

[Billy Darson]

After hitting contact surfaces with weld through primer, and prepping the floor pan for plug welds, would you then lay a bead of seam sealer down on primed contact surfaces of vehicle, put floor pan in place, sandwiching the sealer between metals to be welded?

and would you put seam sealer between the frame rail and the floor pan?  Here's what I have on hand to use. If anyone has a recommended replacement for any of these products please don't hold back. and if you could add what advantage might be gained from the replacement, I would be very grateful.

[89 MJ]

6 minutes ago, Billy Darson said:

So how far would you go on removing the old material knowing that full length pans are going in?

I’m not sure what you’re asking here. Cut out all of the rust, trim your new panels to match the size of the holes you need to repair, then butt weld the new panels in. Use a weld through primer anywhere that you will have spot welds, like where the floors weld to the frame. 

[ThatJeepGuy]

Judging by the materials you've gathered in think you have a good plan ahead of your. Whether or not you seam seal the pans sandwich style and then weld your spots in i think youd be fine. Especially if your planning to hit your seams afterward with a finger drag of more sealant.

 

I've done a couple bumpers now with that por 15. Sanding down rough, hit with etch primer x2, hit with 4 coats of por15 (10 min intervals) and then 2 coats of spray on bedliner (10min split). I would call my work lazy prep as well and its held up very nicely soo i think what you have in store will do just fine.

[Billy Darson]

1 hour ago, 89 MJ said:

I’m not sure what you’re asking here. Cut out all of the rust, trim your new panels to match the size of the holes you need to repair, then butt weld the new panels in. Use a weld through primer anywhere that you will have spot welds, like where the floors weld to the frame. 

My welding skill is not up to par for confident buttwelds on such thin material. Probably should have mentioned that in the post to give better context to the question. 

 

What I'm asking is would you drop the fresh pans in at this stage, assuming all surface prep and protective frame rail coatings have been completed? or would you continue trimming out vehicle metal despite it being rust free? My intent is to keep the new pans fully intact, with the exception of the holes where I plan to plug weld. 

 Much appreciated 89MJ

[Billy Darson]

1 hour ago, ThatJeepGuy said:

Judging by the materials you've gathered in think you have a good plan ahead of your. Whether or not you seam seal the pans sandwich style and then weld your spots in i think youd be fine. Especially if your planning to hit your seams afterward with a finger drag of more sealant.

 

I've done a couple bumpers now with that por 15. Sanding down rough, hit with etch primer x2, hit with 4 coats of por15 (10 min intervals) and then 2 coats of spray on bedliner (10min split). I would call my work lazy prep as well and its held up very nicely soo i think what you have in store will do just fine.

I do intend to do a finger drag of seam sealer.

I was curious if the pan-sealer-frame plugweld sandwich approach was considered "best practice".

Appreciate your input ThatJeepGuy. I assume that you went light on the coats of POR15? all my work is being done without the benefit of a shop, just driveway wrenching in the PNW, so I'm guessing my application intervals will be a bit different. I definitely don't want to be redoing this anytime soon :) nervous LOL 

[89 MJ]

If you have all of the rust cut out, I’d stop there. I bet you could probably butt weld it with a little bit of practice too if you wanted. If you do decide to overlap it, I’d recommend trying to have the overlapping joint be as small as possible. You’ve got a good plan with the seam sealer. 

[Billy Darson]

15 minutes ago, 89 MJ said:

If you have all of the rust cut out, I’d stop there. I bet you could probably butt weld it with a little bit of practice too if you wanted. If you do decide to overlap it, I’d recommend trying to have the overlapping joint be as small as possible. You’ve got a good plan with the seam sealer. 

Yes, Virtually all rusty and compromised metal have been removed.

I had considered practicing buttwelds with some of the material I removed. Ill have to see if I have proper gauge wire for the task. I have an old craftsman portable wire feed MIG welder that I inherited.

From what I could gather from my Uncle's ramblings(career industrial welder) and the interweb, using solid core with CO2 or Argon leaves less slag to mess around with VS Flux core. So ill have to check around for any CO2 cylinders mucking about.

 

once I confirm/acquire proper wire for the task, and get some gas, I'll monkey around with the welder and some scrap for a bit and make a determination on which route I'll take afterwards.  

 

Do you think 3" overlap is too much?  Is the reason for a thin or narrow overlap to be more efficient with the materials at hand, i.e. requiring less sealer on a 1" band VS. a 4" band? or less areas to have worries of rust forming in hidden inaccessible areas? all the above?  

Thanks for your insights 89MJ

[89 MJ]

53 minutes ago, Billy Darson said:

less areas to have worries of rust forming in hidden inaccessible areas?

Primarily this reason right here

[Smash6]

On 9/29/2025 at 3:52 AM, ratrapp said:

definitly get the mj specific pans.i used the xj pans because at the time keyparts hadnt made the mj pans yet.there is alot of cutting hammering and cussing involved using the xj style.i ordered off of keyparts ebay store and didnt have any problems.

 

Farts. I just ordered the XJ half pans instead of the full Keyparts MJ pans to save coin. Oh well, they're enroute. Guess I'm in for some cursing and hammering.

[Billy Darson]

So, after a bit of poking around with a flathead at the rear of the cabin at some of the old seam sealer I noticed there was a bit of rust, and some nearly undetectable paint bubbles. I decided that I needed to cut out more.

 

after cutting, I used a coarse wire wheel to clean off paint and sealer. Flapwheeled any raised weld point after flattening the surface edges with a hammer and makeshift dolly. went over the wire wheeled areas with flap wheel for a cleaner surface. at the end of the day I vacuumed up debris and gave a wipe down with a clean towel. then hit all exposed bare metal with a coat of WD40 to prevent any rust from forming.

 

Next day I sprayed everything that was coated with the WD40 with a dish soap solution twice, with a good rinse after each wash.

Then went after it with the POR15 cleaner/degreaser twice, also rinsing well after each wash.

I blew off standing water and went after the exposed metal with the POR15 Metal Etch. instructions were not clear if the surface had to be dry after cleaning before application of the metal etch. Applied the Metal Etch with a spray bottle, and kept surface wet with the etch for more than 20 min before rinsing. Also instructions do not specify that you should assist in the drying process after rinsing off the metal etch. well I blew off most of the rinse with compressed air before calling it a night.

 

The next morning I see rust staining in patches on the metal that was supposed to have been etched. Nothing major, but enough for me to re-treat the metal with the Metal etch. Probably went through 500ml of the solution throughout the whole process. I might have had less waste if I had brushed it on.... *shrugs shoulders*.  

So now that I have re-etched the metal, rinsed off Metal etch, and towel dried the surfaces, I get to wait until its bone dry before I get to paint. YeeeHaw. so that's where I'm at on this project.

[89 MJ]

Its getting there at least 

[ghetdjc320]

Here's my .02. keep a 1" overlap all the way around. take it down to clean metal and then use 3m panel bond with some clamps or whatever else you need to get it to form a good tight seam (this is crucial to keeping water and moisture out of that seam going forward). Once cured per TDS, add all your welds around the perimeter. If you can pre-drill the new floor pan where the frame support is, you can rosette weld into the hole. If you have access to a deep jawed spot welder, definitely go that route. Also, I'd not use any one part (air dry) seam sealers on the floor pans. You want two part mixing seam sealers ideally. SEM and 3M make excellent medium bodied seam sealer that will stay in place. once seam sealed with 2 part, you can brush on some seam sealer as factory did. Once complete, get a few cans ok 2K epoxy primer (most auto paint stores carry this stuff in rattle cans that have a hardener you puncture before mixing) then use raptor liner, monster liner or any good 2 part coating. Lizard skins is also a good option. 2K basically means there is a hardener that cures the finish vs just air dry. 2K paints and finished tend to be superior in almost all regards. POR15 also works to get down in and seal up thin gaps in seams. You can mask off the back side of the seam then use a brush and brush it down into the seam. 

One little trick I found to remove the factory seam sealer is a multitool with a caulk cutting blade. Works wonders!

 

Edit: generously brush some POR15 into that open frame cavity as best you can and as far as you can reach while it's all open. AMC loved to overlap metal without sealing in-between leaving all sorts of rust prone areas. You have great access to it now.

[Billy Darson]

checked on progress this morning and much to my surprise and dismay, got more surface rust. I was under the impression that the metal etch was supposed to leave a zinc phosphate coating on the metal protecting it from rusting... so what the fudge Did I do wrong?

I degreased exposed metal. rinsed. applied metal etch, rinsed, towel dried, and air dried. so why are there rusty bits? I don't get it.

well any way, Would you continue on at this point or try to do something about the rust? am I just being overly sensitive about minor surface rust?

 

*apparently rinsing off the metal etch is supposed to leave a zinc coating and flash rust. this info was not on the product documentation that came with the product, but instead on the Tube of Yous. So now that I know for sure this is what was supposed to happen I shall proceed with the project.

Ahhh gotta love the inexperience of a FNG. LOL 

Edited Tuesday at 06:16 PM by Billy Darson
new info came to light