Rust prevention.

[Muncher]

Need your guys input on what I should do with my mj. Currently I'm putting the engine back in so I can get back to work and then buy another car to daily. But my jeep is starting to rust underneath and the whole under side is undercoated but it's starting to peel. What would you guys recommend I do to deal with it?

[JustEmptyEveryPocket]

Scrap off all that undercoating. Normally its worthless, and often it CAUSES rust to happen by trapping water. 

 

After all the undercoating is gone, wash everything. Then replace any rotted parts. Finally, get a shultz gun and spray everything down with bar & chain oil. Reapply the oil as needed.

[Muncher]

It did indeed trap water and leave me a nice hole in my floor 

[75sv1]

I'm looking to 'Rhino' line the bottoms of my XJs. Possibly the MJ. I would strip the undercoating. Then treat the rust. I have used POR-15. I am trying some other stuff. I'll have to look tonight. More for farm implements. Then cover that with a 'Rapotor' or Rhino Line type. 

[Pete M]

a thick lining is not better at preventing rust than paint with proper prep. 

[Chad R]

I know a guy that all he does is run his 2005 Chevy truck threw the car wash one to two times a week in the winter, once they start putting salt brine down. The truck has never been garage kept and there is no rust on the bottom, but the key is under body wash.  I am in southwest Michigan I know the pain of watching a favorite car rust away 

[Parei_doll_ia]

Summit has a 2 part epoxy chassis paint that I like

[Pete M]

the insides of the rockers and frames care not for bedliner or car washes.  they will rot if driven in the salt.  

[75sv1]

A local bed liner place does have some stuff for the rocker panels etc. It does not dry hard. I will be giving it a try on two of my XJs. Probably the the MJ and MB 240D. 

[75sv1]

Agriguard is the product. I think you can find it at Tractor Supply.

[87 MJ Chief]

As mentioned above, clean off old product first. Then apply CRC Marine corrosion inhibitor. It's not as expensive as others; spray can application; soaks into tight spaces; dries after 12 hours so debris doesn't stick to it; real world tested with good results.

[ghetdjc320]

From my observation of doin a fair bit of metal and body work on these trucks here are my areas of concern:

most all panels are spot welded together. This creates seams that are not water tight and easily trap water. These seams are everywhere. The factory method to address this was to sloppily apply seam sealer to the inside cab seam around the floor and the floor1firewall transition inside the front wheel well. The seam sealer around the cowl under the fenders is very poor in every MJ/XJ I’ve seen. As it fails, it allows water to trickle into the cab and rot from the inside. It’s quite a crap design in terms of preventing rust. When replacing panels now that used to have a pinch weld seam, I’ve switched to using an automotive panel bonder. Works much better and prevents the issue. If your not doing any panel swaps, take time to go over all the joints with some fresh seam sealer. A 2 part sealer works best. An oscillating tool with an adhesive removal blade will make short work of removing any failed or poorly applied sealer. If you were going to use bedliner/lizard skin or similar, spray it inside the cab after sealing it thoroughly and addressing any rust. Unless you’re doing a rotisserie restoration and going over every seam under the truck, I wouldn’t recommend and type of membrane material (like bedliner or lizard skin) as it will trap moisture in the seams. Paint would be preferable but the downside is it’s chip resistance as the underside will get pelted with stones with normal use. A stone guard type paint would be good there. POR15 actually works very well in this regard but has trouble adhering to clean or painted metal and would require a fair bit of prep. And you must use a good respirator if spraying that stuff as it’s quite vile. The bottom of the bed is another story and it very well could be bedlined with proper prep. Once the finish is done, get a good inner frame sprayer and shoot cavity wax, bar and chain oil, diesel, or lanolin coating inside the frame rails and inside plug holes like the ones located over the rear wheels in the inner fender.