One of the greatest enemys of the hydraulic systems on these Ford tractors is any restriction in the suction side of the hydraulics. The pump is prone to draw in air at the shaft seal and the more the restriction the more air. These pumps won't pump air. It just lets the air pulse and no oil will flow. Even when Ford did put a filter in the later tractors it was in the dump side of the system and under pressure. Not on the suction side.