How about adding a check valve to bleed the air out? Just like your brakes. Submerge one of the fittings with tubing into a jar of the fluid. Pump back and forth, "T" in a check valve and stopcock? Lt the air bubbles come out the "T" the check valve will not let air back in the system. You just need to find a needle valve with a nipple that can allow the fluid out. Maybe one of the Machinists can make such an item?