UPDATE! She lives! spent some time trying to diagnose why the card was dead. Drained and connected up just the cpu, refilled. Tried a 670. Didn't get seen. Removed the vertical PCIE extender and tried again with the 670. Saw it but as a Microsoft Basic VGA adapter. Tried a 1070. Saw it OK. refitted the PCIE extender and tried the 1070 again. Saw it OK.
Refitted the 3080. Saw it! WTAF!
So since I had the card out of the loop, I fitted the Gelid 1.5mm thermal pads, drained the loop, reconnected up the loop, pressure tested, refilled and restarted. Nicehash. Horrible temps. Immediate 90 on both core and ram. WTF?
Drained, removed block. cleaned paste, refitted block super carefully and re-installed. Nicehash. Currently showing core at 1080MHz and 50C with a hotspot of 68.3 and the RAM at 1269MHz and
wait for it
68C! That's 24C lower than with 1mm pads. half a frigging millimetre makes 24C difference.
I'm now worried that my test of the shim was invalid and may have been the result of poor fitting. Not gonna mess with it today as have spent waaaay too much time on this draining and refilling maybe 6 times!