I wouldn’t rely on the poking. Hairline cracks can be absolutely invisible. Aluminum castings are brittle. If you hit it with a hammer and it cracks somewhere else you’ll know they didn’t go through… 
I like the expansion testing, and as said if the ends would be drilled it might expand even less than not at all.
Will check mine in a minute, I‘m curious now!
Please let me know after you check yours. As previously stated four used hubs had cracks in identical spot, so including mine that makes six, but one of the used hubs also had an additional crack half way up the casting about two inches above the bottom one.
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It does not work with ‘bending’ forces, David…
The stress relief from drilling ends of cracks in sheet metal ‘rounds’ off the ends of the crack, and the stress must work on a wider area. With bending stresses in thick material, bending forces must be countered by rounding off the bottom of the cracks - adding end drilling if pertinent for the load directions…
Frank
xj6 85 Sov Europe (UK/NZ)
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With mainly bending forces acting here, the crack getting deeper is more likely than it getting longer…
The depth of the crack weakens the part proportionally - and the inevitable sharp angle at the bottom of a crack is the attack point of the forces. Eliminating this narrow point of stress while probing by removing material to the bottom of the crack is one way…
However, I think the problem is less than we fear - but ‘crack free’ carriers are likely safer…
Frank
xj6 85 Sov Europe (UK/NZ)
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Agreed! They might lengthen still, but in any case if they lengthened they might as well just crack.
I checked the carriers with a flashlight but could not see any cracks. Maybe I made pictures long ago. I‘ll have to check when its on a lift and tyres off - as soon as the transmission mount rubber arrives. If I haven’t forgotten it by then I‘ll make sure to report back.
David
Thanks Dave, they are really difficult to see with the wheel on. When you remove the wheel and clean the front of the hub if they are there they are very apparent. Hairline, jagged, and usually between the flanges. Let me know and I appreciate it.
If you have 6, you could grab the worst one and engage in a destructive test of your own.
belt it with a sledgehammer in a way that would stress the crack, if it breaks along the crack, you have your answer
(this would be of interest rather than throwing them away)
sectioning one with a saw may yield some observations
The four I had were ordered as replacements… New the $ is astronomical.
Used they are $400 to 800 each + shipping. I returned them. If I ever find uncracked replacements I am sure I will run some test on my used ones.
I better gather up the ones I have laying around spare, at least 10
mine are for S1, S2 and 420G, I may have heard there is some slight difference at some stage?
ie a variance in part num, but they seem interchangeable to me
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They are interchangeable, Tony
…the changes are internal - and relevant only if they are to be refurbished…?
Frank
xj6 85 Sov Europe (UK/NZ)
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A hydraulic press would likely be a better approximation to the load exerted, Tony…?
…but crack depth could be probed with a burr…
Frank
xj6 85 Sov Europe (UK/NZ)
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a press would probably be better.
as to crack depth, I am not a metallurgist or engineer, but I do have a belief that a crack in metal does not start without stress, and the if cracked, may break without further warning.
have had a half shaft-snap where the big nut meets a taper, and seen others
Somebody asked about part numbers. The part number listed is C26699 although mine were stamped on the back with part number C26698.
The four replacements I had and returned were C26699.
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Indeed, Tony - and the carrier is also subjected to twisting forces…
Frank
xj6 85 Sov Europe (UK/NZ)
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aint no engineer, but when I dismantle suspensions that I am unfamiliar with, I first make a drawing, showing where all vector forces might be acting, dont want something springing out unexpectedly.
we need an engineer to do the same with the hub carrier, it isnt so easy to understand, but suspect it is probably subject to significant force, and severe road shock would be the area to look at imo
do a bit of 4wd off-road suspension mods, and forces must be understood fairly well, to avoid breakage on the trail
There may be a machine shop in your area that can perform either a dye penetration, eddy current or magnaflux inspection to determine extent of crack if a crack at all or casting deformation.
Gordon
Bingo !!!
Vector forces. And, I am surely not an engineer.
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Bend a bit of metal back and forth enough times and it will crack then fracture.
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In the hubs at hand, we see a crack across the web just above the lower fulcrum. And just under the vertical rails of the structure. The flex point!!! At the weakest part
In my view, unless stopped, the fissure will continue to expand until the part fails. But, that time may never be reached. 30 or so yeas to this point. Will the rest of the car fail before it does!!!
- Decades ago, in my former profession, I was presented with a most interesting claim. As a specialty insurer was my employer, most were!!!
A huge underground water pump for a dry dock at a former naval ship yard. The leased and o0erated by a private company servicing ocean going vessels.
The huge impeller of the pump had failed. The Marine surveyor clime it was because o debris entering the chamber. Cribbage from the dock. tCovered if so, for a ton of money to custom make and set an new impeller. Each a huge undertaking…
I hired an outfit, “Failure Analysis”. The boss took it. A great exercise. I descend into the chamber via a ships type ladder. No place for a guy with a phobia I had none but claustrophobia, sure could exist there!!.
My engineer expert did that vector thing., Using a computer and created a representation. Many arrows across the folded portions of the huge impeller. On points of impact. only folds. That plus the fact that a prior impeller had failed in similar fashion and this one was of a differing alloy seeking to perform better "sealed the deal.\
Not covered as an exclusion and other stuff applied. My inuired and the surveyor were impressed and the declination accepted.
I suspect it also saved them from loss with the navy in accordance with lease provisions. That not my business.
Other than determing an “insurable interest”
That depection of vector forces was instructive long afterwards…
Carl
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Yea the thirty years or so caught my eye!!! These are on a 1985 XJ6, I repeat a 1985
Since this is 2018 your 1985 XJ6 is around 33 years old. This is “30 years or so” like Carl said. I’m confused about “I repeat a 1985”. Did I miss something?
Paul
No your not confused, sorry, I was trying to be cute in repeating my year just to say I am concerned because my Jag is 33 years old and he said it would probably be “30 years or so” before a problem. Next time less cute with my remarks.