SHEET METAL REPAIR
Heavy Mettle: Attacking Rust and Corrosion
We knew when we laid eyes on our 1976 Toyota FJ40 Landcruiser, aka “Tim Toyota,” it had some corrosion issues. After dragging it home and looking deeper, and on occasion through Tim’s sheet metal, it became apparent just how bad it was.
In the past, the lower half of the old rig was completely replaced with 1/8” steel checker plate. Although the FJ40 platform is known for using sturdy steel, it was not known for any sort of preventative measures such as galvanizing or rustproofing to ensure longevity.
Our goal was to patch the various holes in the cabin area and reinforce any brackets that may have succumbed to corrosion. We don’t ever expect to see this truck in a Barrett-Jackson auction with a reserve of $75,000, so a top rate restoration is just not worth the time and effort. The truck will never be original again.
We want to take Tim out in the woods and not have to worry about scraping it up. Besides, in the grand scheme of things, and with the condition that the body is in, we would be better off replacing the entire tub with an aluminum Aqualu unit. With all this in mind, we’re just going to patch the holes to keep fumes and water out of the cabin.
A rig like this old Toyota is a great starting point if you want to try your hand at metal work and panel replacement. The panels are mostly flat, and the steel is nice and thick. This is perfect for beginners and very forgiving when it comes to heat and warpage. There are ways to replace panels without the use of a welder, but why give up an excuse to break out the metal melter, or the reason to go buy one. We wholeheartedly recommend using a wire feed Metal Inert Gas (MIG) setup. Our Miller Multimatic 200 does the majority of all the welding in our shop and when we replace panels, we run a 25/75 gas mix and .030” wire – nothing special.
The first step is to take an inventory of places, panels and pieces that require replacement. Knowing now what you may need will reduce the number surprises later. Start poking around and make sure to check where the rust ends and the solid metal begins. We knew that all the holes we had in the tub were in flat planes and at the very worst, a sharp 90-degree bend. If there is any curvature what so ever, get replacement panels if they are available.
We measured the sheet steel out to 18-gauge in most places and it’s best to match what is there from the factory. There was a powder-coated electrical transformer box that was perfect, so in the name of recycling, we used that. If you don’t have a store of scrap steel, it’s up to you to locate some metal for you to mangle. We recommend any place that sells automotive paints and fillers as they normally have a stash in the back of good, cold-rolled steel.
Now that you have some steel and a place to put it, it’s time to decide how you wish to replace it. We will outline a few ways here, but the basics are the same no matter the method.
Step 1
Cut out the offending metal.
Step 2
Cut your piece to match the hole you just made. Butt-welding will require exact sizing while overlapping patches only need the filler plates to be close.
Step 3
Make sure you have clean, bare steel to weld on the vehicle and your patch panel. You don’t want any weld contamination. We use an Ingersoll Rand 12v cordless die grinder and a cordless ½” wide belt sander. Step 4 Align and weld the panels in place. We have a plethora of magnets, channel locks, clamps and other widgets to keep everything aligned while we tack the panel. Have a small body hammer close by, as massaging the metal into place while it is still hot works best.
Step 5
Once the panel is fully welded in, grind off the protruding weld.
Be sure to have an adult beverage and/ or a good magazine like 4WDrive around to distract you between welds (we’re being serious here). You need to make sure the panel cools slowly and evenly between welds or you’re going to be beating on the panel with a shrinking hammer for days. We know this annoyance first hand.
When welding thin sheet metal, try to use the lowest speed and heat range that your welder can get away with as well as the smallest wire – bringing a bazooka to a knife fight just makes a mess. Although weld through primer can be used as a future rust preventative measure, we have never bothered. We like to use a seam sealer product before the final paint is applied on the backside of the patch. This keeps any moisture out, and seals up any pinholes.
There are multiple ways to attack a body panel replacement job. It boils down to what works for you, your skill level, and the quality you desire for the finished product.
Follow along as we go through three methods of panel replacement, including the rosette welded panel, an overlap panel and a flush weld panel. It’s time to get into the shop and bring that old iron back to life!
Ingersoll Rand www.ingersollrandproducts.com Miller - www.millerwelds.com Aqualu Industries www.hardbody4x4.com
1 You know all those flammable materials and junk you have lying around in the back of your rig? Now is a good time to ditch all that garbage. Once the sparks start to fly, you’re not going to want to be adding any additional fuel to the fire. Cover any windows or glass from sparks as well. 2 The old Landcruiser has been a victim of botched repairs in the past with furnace ducting screwed over holes and sealed with bathtub silicon or duct tape.
3 Our weapons of choice are Ingersoll Rand’s 12V cordless tools including the G1621 polisher we use for grinding down to bare metal; the C1101 reciprocating saw (body saw) that is perfect for slicing out the infected metal; and the G1811 Belt Sander for getting into hard-to-reach places, and finishing up edges on new pieces.
4 Our first panel to be replaced was under the drivers’ seat. Access to the panel and the ability to cut out all the infected metal seemed like a lost cause. We hacked out what we could and sanded as much surface rust out as possible. A rust inhibitor spray was used to try and seal in any additional rot. This is not a “forever” fix and it’s intended to simply seal the cab area. We cut, welded and formed a plate (seen here) about 1” larger than the offending hole. A cheapy pneumatic hole punch was used to create holes that we would weld through and attach the plate to the floor beneath. This is a called a Rosette weld and it works well.
5 The Rosette weld method is of the same strength and style as a factory-spot welded panel. If we, or the next curator of Tim, wish to remove this panel and spend a week repairing it, they will not be cutting out a solid weld from us. We didn’t even have to grind the welds down for this patch and this is one of the bonuses of doing it this way. It’s quick and easy, but is susceptible to future rust and rot.
6 This hole in the passenger side door started out the size of a dime. This is what we were left with once we got back to weldable metal. If replacement doors were available for less than what the Gold Rush crews waste on fuel every season, we would not waste our time patching this lost cause.
7 We created an overlapping patch on this panel because of the extremely thin nature of the metal left in the door. It measured out at about 26 gauge. Using a flanging tool (the same tool used for punching the holes), we were able to recess the patch. We only recommend this method if you’re able to get to the backside of the patch to seal the overlap with seam sealer and/or paint. It is stronger than the Rosette weld, but still not perfect.
8 Taking our time to slowly tack weld around the entire panel is key to keeping it from warping. Forget about “stacked dimes” or any other amazing looking weld bead. These welds should look like that one-night-stand you only remember waking up to (and your friends won’t let you forget).
9 Taking our polisher and flap disk, we ground the welds down and smoothed them out with the rest of the door. Again, take your time don’t create too much heat. It’s very easy to see a warp on a flat panel.
10 Turning to the interior of the FJ40, we had to hack and tear for a while to get to decent sheet steel, then spend more time making the cuts pretty. We are going to butt weld as much of these panels as we can. This will eliminate any overlaps that may hide moisture and the finished product will look better in the end.
11 For the replacement panel, we use an air nibbler to cut the old transformer cabinet to shape. Cut the piece large to begin with and nibble down to size. You want a small (0.5mm) gap all the way around the panel if you can. This gives the filler metal from welding a place to go.
12 As before, tack and move on. Take plenty of breaks and “ask” the metal to move with a hammer when needed. Bashing on it may make you feel better, but it will not result in a better finish.
13 With all the welding done, go back to the grinder. You may find a few pinholes that were missed and that’s fine. Weld them up as best you can and move on.
14 Use seam sealer liberally on all the welded seams from the backsides or in places that will not get any proper paint or body filler. After that, a selfetching primer on all exposed metal is recommended, along with a typical sanding primer top coat.
15 Depending on your level of perfection, you can have the metal repair work you just completed professionally finished and painted, or do what we do and grab a rattle can of matching paint and fog it over the primer. On the underside, we used a rubberized undercoating on top of the seam sealer and primers.
16 We installed some structural support braces to hold the rollbar and seat belts in place as well as some structure for the rear seat mounts. With the rear seats professionally recovered and installed, we are now sealed up and ready to hit the trail without having to be concerned about getting gassed or given a mud bath.