80 Oldsmobile, and I have a spot that has rusted through. The hole started at the bottom where the Landauh top use to stop. I removed the top and am redoing the car now.

1) What should I do first to begin fixing it?

2) Should I weld in new metal? Why type of welder works well to replace metal.

3. Any advice on this?

 

The first step would be to grind down the area to see how far the bad area really is. Next cut out the rust and cut far enough back to get into solid metal. Try to stay with a square or rectangle shape to make fabricating a patch piece easier. A cut off wheel works well. Leave the patch about 1/16" short on all edges so the patch can be placed flush with the original metal and so you can fill that area with weld. Try to shape the patch so it matches the original metal contour before welding as this will save you a lot of finish work. A mig welder is ideal for this type of repair and you might want to practice on a scrap piece of metal to get a feel for doing this. A magnet, that would bridge both the panel and the patch works well for holding the patch in place. You will want to just tack the panel in one place and then do the same in an opposite place. Keep moving around until it is fully welded in place. This will minimize any heat warping of the panel. If you try to lay one long bead of weld on the patch, you will definitely cause a lot of warping. Grind the repair to make everything as flush as possible and again be careful not to build up a lot of heat doing this. Once the grinding has everything flush, put a skim coat of fiberglass body filler over the patched area to seal any pinholes. FG filler is waterproof and will not allow water to come to the surface and cause a problem later. Regular bondo is not waterproof. When the FG filler dries, sand it down with 80 grit. When that is down flush, go over the area with regular bondo and finish as normal. Feather sand the area to taper back the paint, primer it, sand and reprimer/sand as necessary. If you can get to the back side of the repair when it is done, seal it with primer and maybe a little paint. Here is a repair I did to fix an old CB antenna hole that a previous restoration shop tried to repair with bondo and screen. Seriously, they did! They even finish painted the car with this there! Good luck!
Brian

 

Hey thanks for the detailed reply man..I really appreciate it. I used screen and bondo on this area about 10 years ago when I was 20. Short fix, and then I stopped driving the car and begin working on my 72 olds cutlass convertable.

I sanded it down a few months ago and sprayed some paint on it to stop the rust.

I am taking the car apart now to re do completely. It was my first car that I got in 1996 when I was 16. I really wanna make this car one of a kind.

anyways, thanks for the help man!

 

Glad to help out. One more thing....make sure before you do any welding that you have removed the rear seat and interior panels in that area as you don't want a fire. Also, when those panels are removed, look in that C pillar area to make sure the factory didn't spray any foam in there. It's always a good idea when welding where you have somewhat of a closed area to have an extra person on the watch for anything burning and have a fire extinguisher or hose on stand-by just in case. Sounds like a nice project and good luck with it.