oh wtf.
is the system holding pressure when hot?
so just to refresh:
stat - checked twice, both stats good and fitted right way round with joggle valves
- rad, swapped for new quality item
- gauge is a durite one and corresponds with the IR gun
- water pump is working and shaft is firm, vanes all okay and it pumps alright
- matrix okay
- pipes okay
whats in it? coolant or water?
I am at a loss, trying to imagine it in my head is giving me a headache!
HAs it just been sitting idling as opposed to being driven?
I feel your pain, this is one of those odd ones. You do seem to have considered everything. Just to confirm - have you tried running it without a thermostat? Is it actually running as hot as the gauge says? - over 90deg you will have trouble holding onto the hoses.
Did everything go OK with the engine rebuild? Could any engine bearings be binding?. If you take the belts off and the glow plugs out you should be able to turn it over easily with a ratchet on the crank nut. I'm clutching at straws on your behalf
its a good suggestion, could an internal water way be blocked or something?