You did the head gaskets yourself?
Engine still in car or removed?

Impressive amount of work!
Can't say I see anything indicating a head gasket leak on your heads either? I usually see some clean area's in the combustion chamber where all the coolant has blasted off the carbon. Must have been a small seep?
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Yes, finally.
Most if not any of the dealerships don't want to do this sort stuff since it can be an unrepairable failure in some cases with these blocks, and too expensive for most, even at indy shops which also risk doing all the work for a repair that might not work or last long..
Yes, engine was still in place but keep in mind that this problem was in my Range Rover - I only posted it here since it is the same engine as in our XJ.
But considering I have replaced valve cover gaskets & the rear cross-over cooling pipe on our XJ, I see no reason why it wouldn't be possible with the engine in the XJ. I do plan to get to the XJs timing chain tensioners/rails later this year maybe, and that will be easier than on the RR since the XJ doesn't have a belt-driven fan. Not a big thing, but every little bit helps.
I see the inner cylinders look darker & wetter than the two end cylinders on both heads. The front & back cylinders look like they were burning a lot leaner and the center two richer. And with the head gaskets, it looks like the breach was from the center combustion chambers into a small coolant passage on the top side of the gasket, between the gasket & the head, not the gasket & the block. And it looks like it was on the exhaust side of the head on both sides.

 

@12jagmark Did you check the heads and block for distortion? Did your spark plugs provide any indication of rich vs.lean?

 

If you do remove the heads on your XJ I will be waiting for that thread!
Yes I saw the cylinder color differences but they were the same on both heads? Head gaskets leaking on both sides?
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Yes, both heads & the block were flat well within spec.
I was expecting some warpage or possibly a crack, but no indication of anything other than the gaskets breaching between the combustion chamber and a coolant passage on the top (between the gasket & the head.
The spark plugs and cylinders did show indications before I tore into pulling it apart, not too bad though since it was a small leak that didn't appear to get worse over the years.

I hope the XJ never has to have it done. So far so good, with almost 165k miles.
I think the RR overheated with the previous owner. I found that the coolant pump had been replaced before I got it, and I don't think they would've replaced that without a failure.
Yes, both heads appeared to have the same leak, pretty much in the same place on both sides. The center cylinders