Well, after all this time, money, parts and work on Superblack, just before starting her up my tech was checking out underneath in the rear (we had only had her up in front before re: to do brake pads and to r/r the p.s. hoses.) Disastrously, he discovered two major rust-out areas while under there that we had no idea about before. One is the right rear radius arm was completely hanging down free on one end (along with the safety strap), just a few inches off the ground, b/c the supporting segment of the frame above it had completely rusted out and was missing. Another such area found just front of the rear wheel arch. We knew we had a small spot of rust even visible on the body just in front of the rear left wheel, but I had treated it with rust converter (since the body color is black anyway) and it hadnât come back though, so donât know how bad that area is yet.
I really donât understand it. I thought Jag put in all new kinds of high-tech rustproofing beginning with the '92 MY. ??? On a hunch, I had my tech check out the same areas on Superblue, given they are only two years apart but have the same mileage (90K). She was originally a MA/NJ car, btw. He discovered what appears to be the beginning of rust on the same radius arm area which, if it continues over the next few (years?) will likely cause a separation in that area, too. His thinking is that it looks like in the case of both cars the rust (and therefore the wet condition creating it) came from the inside out, esp. since on Superblue the factory rust-proofing coating (black) is clearly present on the outside of that area. The rust in that area on Superblack looks like it just spread like wildfire in that area. Where would water be coming from above those areas to create the rust in same?
So wondering now whether I should just peddle Superblack for parts, and start thinking of selling/trading off Superblue as soon as I can. Obviously someone who is going to buy Superblack wonât be as naive as I was when I bought her, and Iâm beginning to thing twice about my previous policy of always buying my Jags on Ebay. I canât help but think the PO knew about these rust areas and just kept his mouth shut. It looks like to fix those rusted areas she would have to be taken to a frame shop to have the same areas cut out and welded from a donor vehicle, assuming I can find another '92 (or other acceptable MY) to weld in. Otherwise, there would be a lot of custom fabrication, drilling, etc. required of the repair patchwork.
Photos? Iâve read of a few forum members here replacing the part (a cup with bolt hole in it) that the radius arm bolts to, which is bolted to the car, which can rust out.
Or are you simply talking about the four (?) rear suspension mounts, which are known to break apart?
Yes, the âcup with bolt holeâ I believe is what you are referring to, Greg a/k/a âradius armâ. There is a drawing of just that thing on the Classic Parts website, but for some reason I couldnât get it to copy and paste here.
Paul,
Yikes! That is scary looking.
What is the history of the car? Did you get a CARFAX report to see where is has been registered over the years? Was there any record of flood damage?
Etta was about the same. It took about 15 months to get to the state shown here. Complete disassembly, acid dip, some new panels, som fabrication. Now ready for bodywork, painting, and reassembly.
I had the radius arm mount detach on an XJ6. It wasnât fatal. I got a new cup from SNG Barratt (although I found the old one would have been reusable). Cut out all the rusty chassis bit and welder in the thickest metal I could find at Home Depot; and welded the cup on top of that. Slathered it in underseal to hide the amateur welding. It just wasnât that big of a deal
Usually that area rusts out from backglass or quarter window leaks. It would be repairable (if the rest of the car is solid), but labor intensive- and if you donât possess the skills, difficult to find someone to do it properly.
OK, that damage on Superblack is quite intensive. I would part out the car⌠But I donât understand why your tech wouldnât check out the entire car before beginning on expensive work?
SuperBlue looks ok, my XJS has a few spots of surface rust here and there.
Yeah, my XJS (1988 coupe) had a leak on the rear windshield that i discovered which must have dripped down over the years and found itâs way under the fuel tank, which was rusted out. Luckily nothing more.
Iâm with the guys who say weld it up. It is a structural component, holding the rear suspension arm in place, but easy enough to get at (on a lift) to weld a nice chunky patch panel there. Thatâs as long as there is enough metal around the area. The zinc dip on the Ford cars was on the outside, no protection from the inside. My rusty spots have either been coming from the inside at the bottom of the front wings and rear valance. Or on the outside, but in places like the front end of the sills or the arches where gravel sprayed up from the wheels damaged the rust resistant coating.
A full rebuild would be a lot more money than the car is worth now, or in the foreseeable future, but a rolling restoration would be viable to keep it on the road. Maybe time to change the name to not-so-superblack.
A past lister regaled us with the skills he developed in rust repair. Taught himself to MIG weld. Messed with cheaper shielding gases before accepting the fact that Argon was the best.
A nucleur engineer by trade!! This area on a smilar car built in the style of a nucleur vessel. Welded strips to form the cup!!
Eventual fate of the fix not known.
Teddycan!!!
Iâve seen You tube mechanics comment on underside rust in any USA car or truck that is based in snow and salt country. Brutal and commences as soon as the critter hits the road.
I suspect a window weep in the subject cars!!
Aye and nay. .
Fixable, yes. Including superblack. Get a chunk of floor from David Boger at Everyday XJ. He has shipped healthy metal to others.
But, the better is a better chassis. A rust free car with severe mechanical or even fire ills???
I donât like under coat. I think it traps waterâŚ
One You tube rust belt mechanic oiled the underside of his older Toyota Tacoma⌠And, wow, the restore of an older Econoline makes Super Black lood easy⌠check Mistie channel
One is the right rear radius arm was completely hanging down free on one end (along with the safety strap), just a few inches off the ground, b/c the supporting segment of the frame above it had completely rusted out and was missing. 
Another such area found just front of the rear wheel arch. We knew we had a small spot of rust even visible on the body just in front of the rear left wheel, but I had treated it with rust converter (since the body color is black anyway) and it hadnât come back though, so donât know how bad that area is yet. 
It looks like to fix those rusted areas she would have to be taken to a frame shop to have the same areas cut out and welded from a donor vehicle, assuming I can find another '92 (or other acceptable MY) to weld in. Otherwise, there would be a lot of custom fabrication, drilling, etc. required of the repair patchwork. 
) 
