I'm working on a customer's '30 Plymouth and the wheel wells are really eaten up. I needed to replace at least that section and it was covered with old tar-based undercoat, and I s****ed off what I could but it still left quite a bit, especially in the area right next to the quarter panel. These particular cars were built with a complete wooden frame for the body and the body panels nailed on to the wooden frame with about a million little nails, so some panel repairs are a little more complicated than say my Model A - anyway I needed to get the undercoat off so I had clean metal to weld the patch panel to - I tried just about every solvent I had here (except the Brake-Kleen, a very bad choice for metal that's going to be welded) and nothing worked very well, so I ran over to NAPA and found some tar and bug remover in a spray can (Stoner Tarminator) and this with a steel bristle toothbrush style wire brush took it off nicely. The pics are of the p***enger side, which is still in need of repair, and the driver's side area that I'm currently working on - the side of the wheel well next to the quarter is as it came out using the spray and brush, the other side I've cleaned up with a 2" surface conditioning pad. Just thought this might help others.
I believe old under coating is petroleum based, I found a can of elbow grease (the big can) and a gallon of gas worked as well as anything. Warning gas is flammable so don't try this at home..............
I stripped my whole frame, and under body where I need to weld patch panels with an old fashioned paint s****er and a wire wheel on my grinder.
Heat with a propane torch until soft then s****. Comes off pretty easy, then use solvent on a rag to wipe off excess. Wheel wells, floor pans works fine I wouldn't do fenders or any Thinner metal that could warp.
I use a small torch, the type for soldering copper pipes, and a putty knife. Just heat it up and peel it off.
Putty knives,pull s****ers and wire wheels and brushes,I would avoid gas & torches,sure don't want a accident. HRP
I stripped the entire undercarriage of a sixty's GM big car with an electric heat gun and multiple type's of s****ers. Then the residue was cleaned off with a rag and reducer. Took me about a week of evenings after work. Results were great!
oldsjoe nailed it. This is the best method I have found so far. Did this on parts of my 56 and last year on a 32 Ford body. It does take time and lots of muscle but you should be satisfied with the results. If you have other areas where you might want to re-apply some coating, the heat gun keeps it soft and easy to work with. I did this under a right side repaired area of the 32 roof and it looked just like the coating on the left side making the repair look invisible and adding some sound deadening.
i have used both the propane torch and heat gun with good results. too hot and it will smear and leave a residue, too cool and it will take too long. warm the tip of the s****er and keep the heat an inch ahead of the s****er. push faster if it gets too soft.
Probably can't get it unless it is in a "gel" paint stripper. Methylene Chloride! Stuff will wipe the "smile" off Mr. Clean's face! pdq67
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