Posted by: Mark Polk | 2013

71 Power Wagon – Rust a Bad 4 Letter Word

Rust Repair

Rust Repair

Fortunately my 71 Dodge Power Wagon project doesn’t have too much rust, other than the floorboards. The previous owner pop-riveted some metal patches in the floorboards and sprayed the repaired area with undercoating. The first problem with this repair job is the seams around the patches were never sealed properly and the second problem is  I don’t use  pop rivets in a vechicle restoration project.

In most cases rust on a vehicle is a result of water and other elements penetrating a seam on the vehicle and slowly breaking the metal down forming rust. When a vehicle is built all of the seams are sealed with a auto body panel sealant to help prevent water from penetrating these seams. Areas of the vehicle that are constantly exposed to water, salt and other elements eventually give in to this exposure. If you have been around certain vehicles you know the weak areas that tend to rust out. In addition to exposure there are cases where a manufacturer used inferior metal and these areas are prone to rust over time. Enough about what causes rust, let’s get on with the repairs.

I have said before that aftermarket parts for a 71 Dodge Sweptline truck are hard to come by. Most vehicle types offer good aftermarket parts support for restorations. If you need a body patch panel you can order it and have it at your doorstep in a couple days. Not so with old Dodge trucks. I searched the Internet for floorpan patch panels and did find some but they were $160 each. Now $320 for two floorboards seems a little much to me. Granted they did include a stamped section to fit around and repair the cab mount area, but I don’t know if it justifies the price. On Ebay there was a “make a offer” for the floorboard patch panels which I did, and it was abrubtly turned down. So I went to our local steel supply store and bought two 2X2 foot pieces of 18 gauge steel for $12.00.

Step #1

Step #1

The first step in repairing the rust damage is to cut the rusted area out. You want to get rid of all the rust and weak metal and leave about 3/8″ to 1/2″ around the perimeter to weld the new panels in. You don’t want to leave too much overlap because it will be difficult to seal on the underside and will just allow water to get in and start the rusting process all over again. Just mark the area to be cut out and use a cut-off disc in a grinder to remove the old rusted metal. Once the metal is removed it’s important that you grind around the entire perimeter so there is a clean metal surface to weld to.

Step #2

Step #2

Next, I use a material that is easy to cut and that I can see through to trace the pattern for the new patch panel. In this case it was some underlayment I had left over when I installed some new laminate flooring. It worked great. Just lay it over the cut-out area and trace around the outside edges leaving a small amout of overlap.

Now cut the traced out area with scissors and lay the pattern on your new metal. Trace around the pattern and use your grinder and cut-off disc to cut-out the new patch panel. Grind around the edges to smooth it out and prep it to be welded.

Step #3

Step #3

The next step is to weld the new patch in place. Position the patch where you want it and make sure all edges are clean and ready to weld. It’s important that you get a good ground so you can get the best weld possible. Clamp the patch in place and start tack welding around the perimeter of the patch. Don’t run long beads, the heat will distort your metal. Make one inch welds the move to a new area and repeat working around the entire patch. Allow the metal to cool and continue going around until the patch is welded in place. I like to weld the entire patch panel so there is less chance of water penetrating the area after the repiars are made. When the welding is complete you can grind the welds to level the surface off and prep for paint or undercoating product.

In either case (if you weld the entire surface area, or just weld in sections) it’s extremely important that you seal the seams on the top and bottom of the patch with a good body panel sealant. Do not use silicone. Body panel sealant is flexible and can be painted or sealed over with an undercoating product.

Mark Polk

Auto Education 101

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