Hello everyone! Newbie here. Bought a '96 XJ. Pretty great shape, mostly stock (poor man's lift with add-a-leaf and spacers). Paint's in great shape, drives wonderfully, was well maintained, good compression, good cooling, no mechanical issues, ya-de-ya. My first task is tackling the underside and all that dreaded rust from 20 years in the Northeast winters. First owner coated it with what appears to be a very thick, very hard matte black undercoating. Looks like it might have been rolled on/brushed from how thick and textured it is (rear axle pic for reference). It's very resistant to chipping and peeling from some basic poking n' prodding with a flathead. Problem is, there are also some shoddy patches covering what were two sizeable rust spots on the unibody rails in the rear, and I can see hints of rust here and there underneath where some of the coating has flaked or fell off. I'm the kinda guy who needs to see the real **** underneath so I can cut and weld where needed, followed by wire wheel, proper rust conversion and undercoating, but that's a topic for another day.

Any tips on how to best tackle removal? Minor solvents don't make any dent in the stuff, I've been debating between an oscillating tool, heat, and scraping, or using aircraft stripper. Any inputs on what type of undercoating this may appear to be and the best approach are appreciated.

 

I'm a fellow 96 noreaster. Got mine under very similar circumstances. Though mine was covered with what appears to be a cheap rubberized bed liner material. I have not attempted to remove it, but I use Fluid Film, and it has a way of getting underneath the stuff and it has largely finally come off my axles over time.

I'm guessing that is either brushed on POR-15 or some type of bedliner. I don't have a ton of experience in this area, but I'm guessing something mechanical like a portable sand/soda blaster would probably be the way to start removing it.

If it is POR-15 it may be generally working - looks like it has kept things in pretty good shape (based on the picture). POR-15 works by mechanically trapping rust and preventing it from expanding. When rust can not expand - it stops. Good idea in principal, but rust will be prevalent any where the product has failed (patches, areas where original adhesion wasn't good). I'm not a huge fan of "coatings" for the north east, because it only protects one side of things, and the rust just works its way from the other side, and the coating hides the problem until it is severe (bubbling the coating off, etc). So I went the Fluid Film route (basically oiling everything), but once I made that choice I can't easily go back - because getting anything to paint/adhere on over a previous Fluid Film application would be darn near impossible unless it is thoroughly/chemically cleaned. It also means my Jeep is messy to work on. But the product works, so I don't mind the mess.

 

Thick. Hard. Textured. Resistant to chipping, and minor solvents dont affect it...

Could be bedliner. Could be Por 15.

You say there are spots where it has chipped off. Out of those two, my guess would be Por 15. If that stuff isnt applied properly, it wont stick. Ive never dealt with bedliner so i cant say. But it doesnt sound like paint.

 

I would attack the suspect areas only with propane and a scraper. The way it burns of will be indicative of its constituents, and allow you to repair any critical areas first

 

Just use a grinder with a flap disc to get it off on the areas you want to work on.

 

Thanks for the input, guys. I took some aircraft stripper and a wire brush to some, didn't even make a mark -- quite literally, in fact. What kind of sorcery isn't affected by aircraft stripper? I've used it to take the paint off a Stryker.

I think I'll be going with the grinder/wheel/flap disc. Can anyone recommend a good rust inhibitor and spray for getting inside the frame rails?

 

Fluid Film

 

I used this in my '00.

https://www.eastwood.com/eastwood-in...z-aerosol.html

Be frank with you I don't know if it is doing any good. Did it the one time. Also as somebody said I use Fluid Film which that I am very happy with. All part of my "Rust Retardation Program". LOL.

 

Greetings. I understand I am resurrecting an old thread but looking for some help. I don't actually have an XJ, but I have a 2001 TJ, hope you don't mind . I have the same undercoating on my Jeep described in this thread. I think it was sprayed at factory or even at a dealer given some of the spots it is. It made it in to areas that never would've gotten coated somewhere without good access to everything. I don't think it is very common on TJs, but more common on XJs, and thus I found this thread.

Long story short, I live in CA now but I am moving back to the east coast, where I am from originally. I am super familiar with Fluid Film, having used it for 5+ years on vehicles while living back east, and I want to bring my TJ with me and fluid film it - however I am concerned that I will either start taking the undercoating off with the Fluid Film, or it won't do much on top of the old undercoating and just make a mess. Does anyone have any feedback on this? I messaged Jordan directly, but he hasn't signed on for a few years.

Here are some pictures of my undercoating, do they look like what your XJs have?

https://www.wranglerforum.com/thread...spray.2417706/

I have the potential to sell my TJ and get another one without the undercoating further down the line (I have another 4x4 rig anyways) and removing the undercoating is not really a job I want to tackle.

 

Needle scaler. Flap discs will gum up fast.

 

You may want to try brake fluid with a chip brush. That stuff breaks down all kinds of paints