Rust Repair - What would you do with this?

[Nemesis1207]

Some background first of all. So my 80 is in pretty good nick overall, and the frame is rust free. The body has some issues though, with some attempts at a repair by the previous owner. Whoever owned this rig before liked to do some water crossings it seems. However they didn't take the time to check the floor pans for water and lift the drain plugs. With the vinyl floor coverings on this model, that traps the moisture in for ages and leads to rust. I dealt with this on the passenger side floor pan a year or so ago (lockdown project), by sanding things back to bare metal, filling a few tiny holes with an epoxy repair putty, and covering the entire thing with 2K epoxy primer. I also did the entire rear cargo floor, which had some surface rust appearing all over from water intrusion from the rear quarter panel vent, which has now been replaced. I'm happy with how all this turned out. The driver's side (RHD model) was more problematic though. I couldn't address it properly at the time, as the exhaust runs under the floor pan, and I couldn't access the underside without dropping it which I didn't have time to do. There were also layers of crap, like body filler and some kind of grey coating covering a previous weld in repair. It didn't seem like it had been done very well, and there was rust migrating out from under the edges of it all, but it was beyond the scope of what I had time to deal with then. I'm now trying to tackle it, but the situation is worse than I expected.

Here's what I've found after stripping back most of the area:

Underside pics in the next post.

The question is simple: What would you do to repair this? Any and all advice appreciated.

 

[Nemesis1207]

 

[Nemesis1207]

Now that the kids are in bed I thought I'd come back here and add a bit more info to help make sense of the pictures. So the green stuff is the epoxy primer I added around March or April last year. In this area I didn't do as good a job as I did elsewhere. Since I worked out I couldn't do this part properly in the time I had, I cleaned up the edges of the corroded area to bare metal, and slathered epoxy primer around liberally to try and arrest the spread and buy myself some time to deal with it later.

The rust running up the door side of the footwell isn't as bad as it looks from that angle. It's just surface rust, and when I get in there with a wire wheel it should come up as clean metal. I forgot to clean and epoxy prime this bit last time. The floor pan itself is the bad bit. As you can see, there was some pretty cancerous rust there that's corroded totally through, specifically in the channel the floor wires run through and radiating out from there. The panels that were welded in were done very poorly. They didn't drop the exhaust or do anything underneath, because when I got the exhaust heat shields off the underside was about 50 pieces of wire sticking through with big blobs of body filler oozing down through holes, and lots of rusted out paper thin metal jutting out where the original panel used to run. They didn't cut away the corroded areas of the existing panel, they didn't treat or paint anything, and from what I can see they didn't even wire wheel it, they just tack welded some sheets on the rusting panels, lazily filled a few gaps with body filler, smeared some kind of apparently porous grey material over the top and called it done. Of course without the rust being treated, and with the underside completely exposed to moisture, it continued to rust past the patch panels, which also started to develop surface rust of their own.

Now, I could clearly chop out the entire floorpan from a wreck and weld it in. That would probably give the best end result. Apart from my limited skills in welding, which I could work on, the main problems with that are I doubt I'd have the time to get it all done, I don't have a floorpan on hand, and given that I live in Sydney, which is currently in lockdown due to COVID again, I don't have much opportunity to get one right now. I'll probably watch some youtube videos on the topic and try my hand at cutting out a floorpan from the self serve wrecker at some point, and put it on my parts shelf for the future. For now, I'm interested in how to do a better repair than was done here before, without needing access to a wreck. If you had to tackle this with basic supplies, where would you start? Would you remove the original patch attempt and start again? Clean it up and extend the patch? Wire wheel it, fill the holes with epoxy putty, epoxy prime on both sides and call it a day? Honestly not sure which course of action would be best to tackle this one.

 

[JunkCrzr89]

Personally, I would cut all of it out, including the previous patch attempts, and redo it by welding in new sheet metal using whatever stock you can get your hands on for cheap.

 

[Rusty Marlin]

We used to use 55 gallon drums for stock, they are thick enough for the intended purpose and flatten out easily enough.
They make pretty good floor boards.

 

[Pascoscout]

Yep cut it all out. Go back as far as you need to to get rid of the rust. Clean up that kick panel and then coat everything with a weld through primer/paint. Form up a new patch. Ideally you would bead roll it to match the indents in the floor board and end those just before the edge of the patch but if you can't do that then make a way to seal off those channels with something welded in. Maybe a tab bent down at each location and welded through the channel. Paint the edges of the patch where it will be overlapping any other metal before welding in. Use spot welds when joining the patch to the kick panel vs a long bead. If you don't have a spot welder I like to drill a 1/4" hole through the top panel and then mig weld it on a little higher setting than normally required for the metal thickness so it gets good penetration on the lower panel. Start at the center and quickly make a circle around the outside edge of the drilled hole. You can grind off the welds if necessary but it's better to leave them be if you can.

Once it's welded in primer and paint it. Don't forget to use some body seam sealer on the underside where the new patch bends up and attaches to the kick panel. Unlikely that your edge will be perfect so don't want to get dirt and water trapped in there. I always recommend against under body coating for this as it can and will crack at seams and is hard to notice. Seam sealer is easier to see if it's failing and much easier to replace if it does.

 

[Fairgame]

Get an expert to weld in a new floor plate. A quick fix would be to sandwich aluminum chequer plate top and bottom. Lots of silicon and rivets or bolts. There are some seriously talented chaps on this site who could probably fabricate you a drop-in plate?

 

[Nemesis1207]

Thanks guys. I've been sitting on this and thinking about it, and I've come to the conclusion that there's nothing short of cutting it all out and fixing it up proper that'll get me where I want to be. Since my feet aren't falling through the floor, I'm just going to put the floor mats back down and ignore it for the next little bit in lockdown, and sort out a floor pan when I can. I know of at least three carcasses in local wreckers where I can pull a pan myself, which would guarantee I can cut it to cover all the affected areas. Since I'm going this route, I'll cut out the passenger side too, since it had a smaller repair done on it too which while better, wasn't perfect, so I may as well get both pans even if I just put the other on a shelf in the garage for the time being.

So, now I just need to learn how to cut a floor pan out, and how to weld it back in. Fortunately lockdown gives me lots of time to browse youtube!

 

[Fairgame]

Thanks guys. I've been sitting on this and thinking about it, and I've come to the conclusion that there's nothing short of cutting it all out and fixing it up proper that'll get me where I want to be. Since my feet aren't falling through the floor, I'm just going to put the floor mats back down and ignore it for the next little bit in lockdown, and sort out a floor pan when I can. I know of at least three carcasses in local wreckers where I can pull a pan myself, which would guarantee I can cut it to cover all the affected areas. Since I'm going this route, I'll cut out the passenger side too, since it had a smaller repair done on it too which while better, wasn't perfect, so I may as well get both pans even if I just put the other on a shelf in the garage for the time being.

So, now I just need to learn how to cut a floor pan out, and how to weld it back in. Fortunately lockdown gives me lots of time to browse youtube!

Personally, I would rebuild on a good second-hand frame. Now that's a project!

 

[FMC80]

Jk, I have nothing else of value to add.

 

[Nemesis1207]

Haha! All good, this rig works for a living, it's not a showpiece. End result just needs to be functional and done properly, it doesn't have to be pretty or invisible. I didn't even bother painting the epoxy primer I laid down last year. I might eventually touch up some bits with a rattle can of white paint sometime, but probably not.

 

[Nemesis1207]

Bumping this thread now since lockdown is over, and I've tracked down a good looking floorpan in a wrecker nearby. $80 for the whole front floor, as long as I cut it out myself. Any tips on the cutting process from anyone who's done this kind of thing before?

 

[A2ShedsJackson]

Thin cutting disk/cut off wheel on an angle grinder.

 

[Couve Cruiser]

I had to do a significant repair on both left and right floor pans. Perhaps more lower firewall than floor pan. After watching a variety of body repair videos, I decided on a method using fiberglass cloth saturated with POR15. I put a layer of cloth on the inside and once it was dry I put a layer of cloth on the outside, overlapping the metal by 1-2" . Once the epoxy based POR15 dried it turned the cloth into a hard and strong surface. The POR15 also strongly bonds the cloth to the metal edges of the repair area if the metal is prepped well. After the repair set thoroughly, I applied a layer of Dynamat on the inside for additional protection. On the exterior of the repair I applied a few coats of rubberized undercoat. It's probably not the MOST ideal repair method, but I'm pretty satisfied with the results. It's holding up well after quite a bit of travel on rough roads. My repair didn't have to extend up the side of the footwell. It may not work as well if a 90 degree corner is involved. Might be an option for some people who have the common rust damage on the lower fire wall due to the rear apron mounting point that retains water.

 

[Couve Cruiser]

Pics didn't work out on the first post

 

[Pascoscout]

On cutting out the donor floor pan you can use the cut off wheel as suggested. Another option is to get a spot weld cutter and drill out the spot welds holding the piece you need in. I'm not familiar with how the floor pans are attached in the 80 series so it might be a single formed piece, in which case the cutoff wheel will be your best bet.

Try to get about an inch more on all sides than the part you are replacing. When putting the patch back in you can either butt weld it or you could get a flange forming tool (the Harbor Freight version works ok) and make a flange all the way around your donor piece. This allows you to use a bit more weld and make a stronger connection than a butt weld. If you go the butt weld method get yourself a set of flush panel clamps.

https://www.eastwood.com/intergrip-panel-clamps-set-of-4

They help keep the two parts even and also force a small gap which helps the strength of your weld and reduces warping resulting from the expansion of the metals when heated.

 

[Nemesis1207]

Bumping this to say I'm planning to have a shot at removing the front floor pan from the donor vehicle sometime in the next couple of weeks. Here's a few very bad pictures I snapped at the wrecker:

Hard to tell from these awful pictures, but this pan is in good condition. Under the dirt and rubbish, there's no signs of rust I can see. It's a perfect match for my HZJ80, same Toyota part number as confirmed via VIN lookup, except of course this one is in red. I figure having that sitting under my floor mats should add at least a few HP, right?

My current plan is to drill out the spot welds along the sides, which I gather should free the panel along the two edges. I'll then attack the front and back edges with a reciprocating saw, at least a few inches beyond the section I need, to free the panel. I'm planning to take out the entire floor pan as one piece, tunnel and all. I figure I can change my mind and cut it down later if I want to, but I may as well take the lot since it's all there and intact.

Any tips and comments welcome. The current plan is to get the floor pan and put it on ice in my shed. I'll worry about cutting up my actual rig and installing the replacement at a later date.