hmm ,did you pull the fluid through one of the rear bleed valves with a syringe type tool,while the others where shut? or just push through with opening and closing the valve?(this will take yonks to do!),

i done mine by this method,and it filled up quick enough. ,when its pouring out ,it seems like its not getting a chance to fill the pipes and air is bypassing as the fluid goes in.

try one rear side first,(do you have a bleed pipe helper-make sure its filled with fluid and submerged in some to stop it sucking in air too!)