I'm very familiar/mechanically inclined with much of anything I need to lay my hands on - except rust. I have no experience repairing or helping to prevent rust. I have no clue if the rust that I have is bad or I'm overthinking it. Here are a couple example pics, pretty much the whole underbody is like this. I bought the jeep when I was in college so I didnt really take a gander under it then since I had no intention of keeping it forever. But thanks to the forums I've been bit by the bug

I'm at the point now where I'm able to put some money into it for needed repairs and wanted upgrades. My question here is, is the rust that I show in the pics at the point where I should sell this one and pick up another XJ from down south to build up, or just flap wheel this and shoot it with some underbody coating? Seems like taking a flap wheel to it will be a ton of work given all of the angles and corners. These pics are from under the driver-rear of the car, looking up from approximately where the brake lines are running.

It doesn't seem to be rusting through anywhere (at least on the underbody, rust on my doors and rockers are at the point where I've made plans to cut and weld in some new sheet metal in. ) so I believe it's just on the surface but I'm looking for some expert opinions before I put money into building it. Any car at 15 years old will have it, but would this be worth fixing?

Yeah, my rear diff is leaking from somewhere. It's on the fix-it list

 

I would leave the underbody as it is. No sanding or undercoating. If you can't poke a screwdriver through suspension attachment points, you may be OK for now.

Your worst problem, and the most critical, sounds like your rockers. They are very structural.

If your doors are not sagging, and are opening and closing well with even gaps, you might save the Jeep. Be sure to really brace it up before cutting rockers. Only do one side at a time.

The only way to kill rust is to cut out the bad metal and replace with new. Anything else, and you are merely delaying the inevitable for a little while.

 

Well it's sounds like you are welding so anything is possible. Most of your pics show surface rust. I wouldn't do any undercoating since that just seals in the rust so it can keep eating the Jeep in private. I would wire brush what you can and spray what you can't with POR-15 or Rust Reformer. As mentioned above its not permanent but what's the harm in slowing it down? It took a long time to get that way, so scrub and spray may be better than you think. If you are building a monster, it's cheaper to start with a rust free vehicle. If it's your buddy and you just want to upgrade a bit and keep it then weld what you can and spray what you can't!

 

My brother-in-law used some POR-15 on an old Chevy truck. The rust continued to eat away in private. He ended up with a real mess on his hands.

I told him not to use that stuff. He believes me now.

Leave the underpans alone. Don't scratch on them. Don't coat them with anything. Not even paint. Let them "breathe".

Do the rockers.

 

Hadn't heard that before from anyone with POR15, good to know.

 

Is it worth fixing? Probably not. These XJs aren't hard to find, and if you want to build one, it might pay you to start clean.

If all you're looking for is a project, you could always open up the frame rails to get at any rust in there with a sand blaster. That would definitely not be worth the effort though if you're able to invest in a rust free Jeep.

 

Is it easier to buy another one? Sure. But if this is a Jeep you've got love for, nothing I'm seeing is beyond a little work. I restore vintage mustangs for a living, fighting rust is a way of life, lol. Sounds like you're comfortable with a welder, so I'd say go for it!

It doesn't matter if you use por15, krylon, or latex house paint... If you seal in rust, it'll keep rusting. You need to see nothing but shiny clean metal before you cover it with anything. Most of the work just requires patience, seams and enclosed areas(inside framerails, etc) take a bit more effort & cutting for access.

The rockers ARE going to be a challenge. They're constructed of layers of sheetmetal rather than one heavy piece. And like anything else, it usually rusts from the inside out, and needs to be repaired the same way. Or replaced if you've got the confidence to tackle that. Either way, brace the hell outta the jeep before you start.

So think it over, you can sell it and not have to deal with this rust, and buy another Jeep(somebody else's rust). Or fix this one, and rust-proof it far beyond the halfhearted effort the factory made.

Check and clear all drain holes, think through your ride's stance, add drain holes at lowest points if/where it suits you.

And my favorite recipe once I've got clean shiny metal...

1) acid-etching primer(get a good respirator, that stuff is hell on lungs), spray it heavy and let it run into any areas you might not have been able to get to thoroughly.
2) let it cure and breathe for 12hrs out of the weather(not a sealer).
3) follow that with a good sealer-primer, let it cure overnight.
4) beige seam sealer at all seams and creases.
5) lightly scuff, and hit everything with Eastwood chassis-black, 2-3 coats half hour apart

Have fun!

 

I've had 23 classic Mustangs that I've taken to various stages of restoration, one late model, and worked on other people's vintage Mustangs.

So yes, I am woefully familiar with rust, too.

 

Ya, it's the biggest issue we deal with. On the rare occasion a Stang rolls in that's truly rust-free I wanna do cartwheels! I had to do full floors & rockers on an '88 GT recently, that made me feel old, lol.

A lot of work ahead on that Jeep, but it's a great feeling when it's all done!