This piston is the moving element inside the power steering pump that converts hydraulic pressure into mechanical force to assist steering. It reciprocates within the pump bore, directing pressurized fluid to the steering cylinder based on input from the steering valve. Wear on the piston bore or seal face reduces pump output, causing heavier steering effort and intermittent assist loss. The original AGCO component is machined to the same internal clearance and surface finish as the pump housing, which maintains the correct volumetric efficiency without bypass leakage. On reinstallation, ensure the pump housing bore is clean and free of scoring, and replace the pump shaft seal.