Guys, FYI
I have 2002 ARX with standard suspension and I had this very same issue. It was definitely a fatigue crack. On my car the fatigue crack grew quite a long way towards the front and back of the car before the shock top finally ripped out on a pot hole just like Matthew. however for at least a year beforehand I could hear a rattling / tinkling sound coming from the back but could not for the life of me find it - until it ripped out of course!
about 6 months later the other side started tinkling, so I knew exactly what it was this time around.
As Matthew showed, there is absolutely no access from the top. structure of the car completely excludes access.
to fix, I snuck two bits of 5mm plate above the mount, with captive studs tacked to the plates, one each side. couldn't do it in one piece of plate since it won't go up the hole. in my case the fatigue crack had propagated towards the front and back of the car quite a distance and intersected the hole in the middle, which is stiffened by an upward fold. crack had progressed right through the fold. so gouged out the crack and welded it closed, added the plate above then added a strip of something like 4x10mm flat bar rolled into a cylinder and welded that to the inside of the hole to reinforce the folded edge.
it was fiddly, but not terribly difficult, certainly not nearly as challenging as fabbing the 3" the intake pipe
no problems since.
I'm about to order BC's myself since the standard suspension is ready for the bin.
my car has done about 180kms, the top mounts ripped out at about 150 and 160k's respectively.
I don't suspect lack of travel positive or negative travel on the BC's on Matthew's, since it happened on mine with standard suspension. you can even see the fatigue crack heading forwards on the photo posted earlier in the thread. What may be a more interesting coincidence is that no one else seems to have had this issue accept Matthew and I, and we both drive early ARX's. Is there a chance that this top mount is different on the ARX since it is a bit higher than everyone else?
How did the eng shop fix your top mounts Matthew?
Lenny.