Hello all FTE, I am wondering where I should remove metal on my driver side wheel arch on my 84 F150 before I put a patch panel form LMC truck on. I recently bought this truck with very low miles and the only rust on the truck is on the driver's side wheel arch and the bottom corners of the bed. Therefore I am trying to shore up any issues so I can keep it in nice shape. Even though the rot only is on part of the wheel arch I am planning on cutting out a large rectangular section to be replaced. Do i need to remove this much metal? Also the inner fender has a small area that is rotted and I am wondering if more of it should be removed as well.

 

 

i usually go rot plus 2 inches on large panels to ensure good solid welding point.
as long as you remove to solid metal you should be good to go.

 

I have removed the section of wheel arch panel that was rotted. The good news is that the inner fender seems to be mostly intact. I plan on cutting the repair panel down to size so it is basically flush with the truck and lining it up with the lower lip of the inner fender. I am also thinking about cutting away the rotted section of the inner fender ans then make a patch from sheet metal from the hardware store. Is this a good idea?

 

yea, that will work. just make sure everything is sealed and painted very good or it will only rust out again.

 

I was planning on doing what I did when cleaning up rust on my floor pans from water leaks where I use a phosphoric acid type treatment called Metal Prep & Etch to treat the surface rust and the apply Rustoleum flat black paint. Will that be enough to stop further rustig of the inner fender or do I need to do more? I have heard of using an epoxy primer but my knowledge of paints and bodywork is limited.

 

i also use the prep and etch, but i put a good coat of rustolium red oxide industrial primer before i cover everything with rustolium industrial paint, then a good coating of spray on bedliner to permanently seal everything..
visible exterior surfaces ger regular PPG base coat /clear coat.

 

When I cleaned up the surface rust on edges the floor pans I used the prep and etch, then painted with flat black, and then coated with rubberized undercoating. I hope that was sufficient since that area doesn't face any friction and I sealed up the water leaks.

 

that should work . i like to use the red oxide primer before painting though.
just a preference from doing body work for years.

 

Is that industrial primer available at most auto parts stores like NAPA and Oreilly's?

 

don't know. i get it at lowes or home depot.

 

If It is not too expensive I am going to have a guy weld the new panel in place for me since all I have is a flux core welder. I am thinking that welding the repair panel just under the holes for the trim piece that attaches here will allow me to reduce body work since the welding bead will be hidden under the trim. The vertical seams on each side will have to be ground down however. I am unsure about the bottom of the panel where it meets the inner fender since it was spot welded originally. I might have to use auto body epoxy to secure that area.

 

if you are going to have a pro do it, he will most likely have a spot welder too.

 

Would using the trim be a good way to hide the weld?

 

I would worry less about what the trim may or may not cover and more about access from the rear side for planishing out your welds. The welds and HAZ will shrink, the unaffected panel about 6" or so away from the weld will try to remain flat, and the area between the two will form a wave as these two opposing forces react on it. You fix the shrinking issue by planishing (stretching) the welds. If your patch is taller than the trim area, you'll likely have more room for an easier job of planishing with hammer and dolly the farther up you go. The better job you can do in planishing, the less filler you'll need. Having a larger hole on the outside will also help you to get better access for fixing the inner wheelwell while it's open.