If you require that much volume it would seem the rear brakes are too far off the drum. Disc brakes ride the rotor so that is not where your volume is required. If the rod is not the correct length of the MC is not spaced properly you may not be allowing the MC to draw fluid. That is where the spacer comes in on mine. It wouldn't pick up fluid to bleed until I let it back off the adapter plate about 1/4 inch.
