DIAPHRAGM 4798400 - Caterpillar

operational checks can be used to find leakage in the steering system. Also, the operational checks can be used to find a failed valve or a failed hydraulic and steering pump. Before you begin the checks, refer to Systems Operation, Testing and Adjusting, "Machine Preparation for Troubleshooting". The oil in the steering system must be at an operating temperature of 46 to 52 °C (115 to 126 °F).Release the parking brake and place the transmission direction and speed control lever in the NEUTRAL position.
Release the service brakes. Turn the steering wheel in both directions until the steering cylinders extend completely and the steering cylinders retract completely. The extension of the steering cylinders must be smooth and regular. The retraction of the steering cylinders must be smooth and regular.
Listen for noise from the hydraulic and steering pump.
Inspect the steering system for leaks and damaged components.