I am using vacuum bleeder. When I bleed the master cylinder using the bleed ports, (opposite side of the break line connection ports) fluid flows out of both the front and back reservoirs and into the vacuum collection bottle. When I vacuum bleed the brake line side of the master cylinder, brake fluid flows through the break line port of the rear reservoir but no brake fluid flows out of the front reservoir brake line port. I next reconnect brake lines and apply vacuum bleed lines to both boosters, using their bleeder screws. I can vacuum pull fluid from the rear reservoir through the break lines, through the front booster and out of the front booster bleeder screw. However, when I vacuum bleed the rear booster that is supplied by the front reservoir, I can't get any air or fluid to move through the booster and out of the booster bleeder. Is this master cylinder defective?