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Posting this to tell the story of my experience to repair rust on my iroc with body repair inexperience and my learning lesson with flux core vs mig welding.
I hope this will help others looking for help in the future as this is a common rust rot area on third gens. I did alot of research, and found alot of useful information but it was buried in users build threads in the members Camaro/firebird forums. So if in anyone wants to add what I did wrong and what I could of done right to help others in the future, please do so.
this all started when I found water on passengers floor after washes or rain. I researched and found old cracking seam sealer on the fire wall was best case scenario for cause of the leak.so I pulled back the carpet and fire wall insulation to repair the sealer but instead I found this.
looks like the cowl rotted through for some reason and was the real cause of the water leak. Suddenly I had a worst case scenario on my hands. Had to investigate further to see how wide spread the rust was. I pull off the passengers fender, power antenna, and cleaned off all seam sealer. What I found was the cowl drain on that side had plugged up with 36 years of leafs, dirt, and debris which caused the water to sit in that low spot of the cowl and rot. So I took a pick and started poking at it to see how bad it was and sure enough the rot was multi layer deep and damaged several panels that met at that location.
But I couldn’t see if the rust got through the fire wall.so I removed the ac and ac box, sure enough the rust rotted right through the cowl and fire wall right underneath the ac box. So I did my research and found I had to get into the cowl to see the full extent of the rust and since the rot was in the corner I was going to need space to work so I decided going in from the front was the best way to go. At this moment I reached the point of no return and started cutting into the body with an angled die grinder and 3 in cutting wheel, had to cut some spot welds but alas I made access to the cowl.
Close up of what I found and the worst of the rust.
Next I cleaned up that section of the cowl and found some more rust up towards the center hiding under the paint. To fix this I was going to have to cut up two good sections of cowl/fire wall. So I removed the carpet, seats, center console, dash, heater box, and finally air circulation door. To my relief the rest of the fire wall and most of the interior was rather spotless.
The passengers floor board is rusted, which was to be expected from the water leak collecting here.
cleaned up the rust and removed all the rest of the seam sealer to make sure nothing else is hiding. To my surprise everything else was in good condition, even the floor wasn’t that bad compared to the stuff I see on this forum.
The floor will be treated and sealed to be tackled some other time. For I’ll go after the cowl because it seems the hardest and body shop wants to much to fix.
Here is we’re the battle and learning curve started. I had experienced welding in high school shop class and at other previous jobs but I wouldn’t say I was good at it. Non the less the metal is fairly thin in this area and would only take a series of spot welds so I was confident it would be easy. Boy was I wrong.
my garage is wired with 120v/20a only so a MiG welder like the ones I have experience with wouldn’t work and I didn’t want to spend over $1000 on a welding rig plus shielding gas that’s more than I paid for the car lol. I started searching for cheap diy welders and found many posts and videos of people using harbor freight flux core welders. My coworker had one so i tried to practice with his and I hated it, was super inconsistent and couldn’t get good penetration with it. I researched for better quality welder and wire, found this forney fc140 would be a good try at only $250.
It was an impressive little welder with a better build quality than harbor freight’s and a lot more consistent with better welds. A lot of videos and posts said Lincoln flux core was the best but I found forneys wire to be better.
I went searching for sheet metal, I measured the pice I cut off and found it to be somewhere in between 20 gauge and 22 gauge. The closest I could find in my town was 22 gauge at ace hardware. I practiced after work for a week and was happy with my results, I started trying to fab up a patch panel and quickly realized how hard it was going to be because this piece has compound curves in different directions. As soon as I would try to butt weld it the curves I formed would go out of shape from shrinkage and pull the patch away from the opposite side creating a gap that flux core will just blow through. I irritatingly learned flux core butt welding can not have any sort of gap and both panels will need to be tight to each other or it will blow through because of the heat. Even turning the welder down and using the thinnest wire at .030. At this point I realized I was going to have to lap weld the patch panel on from the inside. I made a few panels and only one worked, this was the best I could come up with to much disappointment.
I spent several weeks going to three pick n pulls in the cities hours away. Only found four third gens and all had some sort of rust or rot in this area. So donor panel was out of the question and I’m just going to have to live with this patch for now.
Tough to find good panels to replace these areas. There aren't many of these cars left in the junkyards and many that are have the same rust issues. Most of these areas are not too difficult to cut and shape out of new sheet metal, as you did and yours looks pretty good. A set of body hammers and dollies, sand bag and a vice will work for most of what you need to shape. More complex shapes you may need to make it out of multiple pieces and butt weld them together.
Don't worry too much about what the weld looks like. A lot of it will be ground down and/or covered with seam sealer anyway.
As for the welding, using gas instead of flux and also 0.023" wire instead of 0.030" wire will be a lot easier to do a good weld without burning through the metal.
Good job. GTA is right though, Argon/CO2 makes a much nicer weld and .023 wire is the way to go. I got almost 40 years of fixing cars under my belt, and I'm I-Car platinum certified and I still hate dealing with rust.
Keep practicing and you'll get it. You're not in a critical structure area so you'll be fine as long as you get it all sealed up!
I am starting work on a similar problem except that mine is far worse. Mine is rotted from the seam at the upper firewall all the way down to the toe board just ahead of the front seat mounting rail. No donors in the pick n pull yards anywhere near Washington State, however, I got lucky. All American Classics in Vancouver, Washington has about 12 or so thirdgens. They cut me a full car section from just in front of the seat mounting rail all the way across the car and just in front of the firewall all the way across the car. Only cost me $200 and I can just cut patch panels from the donor section when I get the time. They do ship parts if you need something more for your project.
That area in the passenger wheelwell/cowl/toeboard is also very common. I did the same repair on mine. It's multiple layers of sheet metal that come together and a ton of seam sealer that ultimately fails and lets the water and road salt into the seam, rotting it out. Though, it's not a hard area to fix since the metal is simple shapes and relatively easy to fabricate. The rust areas you are finding are some of the common spots and I suspect you have more in the other common spots. I would be looking at the front rocker corners, front shock towers, rear inner and outer wheel wells, lower quarters under the ground effects and rear bumper mount. Some of it won't be obvious until you start poking at with a sharp object. I went through this a few years back with mine. I thought I was done with each area I fixed and I kept finding more. My restoration thread might help you.
I am starting work on a similar problem except that mine is far worse. Mine is rotted from the seam at the upper firewall all the way down to the toe board just ahead of the front seat mounting rail. No donors in the pick n pull yards anywhere near Washington State, however, I got lucky. All American Classics in Vancouver, Washington has about 12 or so thirdgens. They cut me a full car section from just in front of the seat mounting rail all the way across the car and just in front of the firewall all the way across the car. Only cost me $200 and I can just cut patch panels from the donor section when I get the time. They do ship parts if you need something more for your project.
dang that’s awesome wish I would have known that. I’ll keep them in mind if I need to go at it again some day. Thanks! Good luck with your endeavor.
That area in the passenger wheelwell/cowl/toeboard is also very common. I did the same repair on mine. It's multiple layers of sheet metal that come together and a ton of seam sealer that ultimately fails and lets the water and road salt into the seam, rotting it out. Though, it's not a hard area to fix since the metal is simple shapes and relatively easy to fabricate. The rust areas you are finding are some of the common spots and I suspect you have more in the other common spots. I would be looking at the front rocker corners, front shock towers, rear inner and outer wheel wells, lower quarters under the ground effects and rear bumper mount. Some of it won't be obvious until you start poking at with a sharp object. I went through this a few years back with mine. I thought I was done with each area I fixed and I kept finding more. My restoration thread might help you.
thanks, I did a lot of research before I started and made sure I wasn’t going to put in money or effort on a pile of rotting junk. The only rust I found was the battery tray, a pillar, and rear bumper bracket. Thanks for your build thread by the way, it’s one of the threads I bookmarked for reference and planning. A lot of good info there, I decided to make this thread here to help people looking for this in body like I did only to find what I needed buried in build/restoration threads. Your work is great by the way love your build.
At one point I was walking through Home Depot and found the Lincoln electric 140 was on sale for $499 normal $699. Came with a spool of flux core and .025 MiG wire, gas hose , and regulator. Picked it up and sold the forney to a friend for $200. Went to harbor freight and bought a cheap weld cart, rented argon/co2 bottle from a local supplier for $60. Not bad for this little set up I’d say.
Man what a night and day difference, so much easier and forgiving with gas. Wish I didnt waste my time messing with flux core.
It got difficult here with the different directions and curvatures this piece needed. I kept on fighting shrinkage and warpage, I tried going to a thicker metal but that was harder to shape with my skills. I tried to go to thinner sheet metal and tack it in and form with hammer and dolly a tack a time but that also caused issues.
Tried to save this panel as best I could. I cut the rust off the bottom and welded in new metal the side piece and upper piece were also cut off and new metal welded in.
Looks good. It’s tough not having NOS or reproduction sheet metal available. Sometimes the only way to do it is to rebuild it with multiple smaller pieces, as you are doing here. Once it’s painted and seam sealed, it will be hard to see unless you know what you’re looking for.
