651E and 657E Wheel Tractor-Scrapers Hydraulic System Operational Checks Caterpillar

The operational checks can be used to find leakage in the implement system, the cushion-hitch system and the push-pull system. Also, the operational checks can be used to find a failed valve, a failed implement pump or a failed cushion-hitch pump.

Note: Refer to Testing and Adjusting, "Machine Preparation for Troubleshooting" before you perform the checks.

Start the engine. Operate the engine at high idle until the hydraulic oil reaches the normal operating temperature.

Checks for the Implement System

Extend the implement cylinders and retract the implement cylinders several times. Allow the implement cylinders to travel full stroke in each direction.

1. Watch the cylinder as the cylinder is extended and retracted. The movement of the cylinder must be smooth and regular.

2. Listen to the implement pump for noise.

3. Move each control valve into the HOLD position while the implement is off the ground. Watch for cylinder rod drift. If the cylinder moves more than 19.0 mm (0.75 inch) in 60 minutes, then the cylinder drift is excessive.

Implement cylinder drift is caused by oil leakage in the following components:

• Cylinder piston seals

• Line relief valves

• Lock valve in the main control valve

Checks for the Cushion-Hitch System

Turn on the cushion ride. The rod of the load cylinder will extend. The rod should extend approximately 190 mm (7.5 inch) in less than one second. Slowly, the rod should then drop into the cushion ride position.

Extend the load cylinder and retract the load cylinder several times.

1. The extension of the load cylinder must be smooth and regular. The retraction of the load cylinder must be smooth and regular.

2. Listen for noise from the cushion-hitch pump.

3. Allow the load cylinder to extend to full stroke and allow the load cylinder to retract completely.

Checks for the Push-Pull System (If Equipped)

Extend the bail cylinder and retract the bail cylinder several times.

1. The extension of the bail cylinder must be smooth and regular. The retraction of the bail cylinder must be smooth and regular.

2. Listen for noise from the cushion-hitch pump.

3. Allow the bail cylinder to extend to full stroke and allow the bail cylinder to retract completely.