underbody rust repair?

[Jevik]

I'm looking at purchasing my dads 2003 impala but it will need some repair on the underbody. I can weld but how far around the affected area should I go? I will be welding in all new material.

[idrivejunk]

Depends on what you're able to make with what you have. If you can re-create the entire piece or buy it new, do that and you'll only have to make plug welds. Cut your welds from the top to make life easier. If all the rust is in one spot, just cut the weak metal away until you find where its solid. Try to get ALL the rust cut out, then just patch the hole. The pic isn't much help, only shows one side. Just be sure to use the correct gauge metal to retain structural integrity and be sure to paint the inside of that rail to prevent a repeat soon. Cutting your part from a donor vehicle would be a great idea in this case.

[bobc455]

Since rust is frequently common in the same areas, is there new metal available (for example, for the jacking points)?

I've heard about "rocker panel replacement" but I'm not sure if that stuff can be purchased new.

[NebTurboST5]

take a portable plasma to a walmart parking lot...free replacement parts...

[Sven the Sexman]

take a portable plasma to a walmart parking lot...free replacement parts...

He lives in NY...where the car can be rotted in half but as long as the SES light is off he passes inspection, so Wal-Mart parking lot repair panels probably won't help much here. There are some replacement weld in panels available for the GP's, but I'm not sure about the Impala. You can do a temp fix and cut out the rust and weld a patch in...it'll last ~ a year. Replacement of the entire panel works better and lasts a bit longer. Just remember anything you buy for a repair panel is going to be cheap Chinese metal and won't last nearly as long as stock.

[bobc455]

Sorry to hijack the post, but where can you get these panels? Or is it something that a body shop has to do?

[Sven the Sexman]

Sorry to hijack the post, but where can you get these panels? Or is it something that a body shop has to do?

For GP's and Impalas, you can buy the rocker panels from Rockauto. Make sure they are 100% cleaned before install. Use a good weld-through epoxy primer on the back side to help keep corrosion to a minimum. I'd drill a 1/4" drain hole every foot or so and spray undercoating in there when it's all welded together so that it will also help prevent rust then put rubber plugs in there when done so you can clean them out periodically.

[idrivejunk]

Sorry to hijack the post, but where can you get these panels? Or is it something that a body shop has to do?

The panel shown is a part that is probably only available new as part of a floor assembly which is way more than is needed. Fabrication is the most likely answer since the OP is in a rust-prone area. I work at a shop and would probably want two labor hours to fab the piece and another two to put it in and do a nice job. Thats with whatever interior flammable stuff is on top removed. A person who welds at home but has no metal brake for fabricating could cut out the section and take it to a local sheetmetal fab place and have it made. That also tends to cost a little more than you would think. Even with just a bench vise, the part could be shaped with some patience.