539 Knuckleboom Loader Hydraulic System Caterpillar

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Personal injury can result from hydraulic oil pressure and hot oil. Hydraulic oil pressure can remain in the hydraulic system after the engine has been stopped. Serious injury can be caused if this pressure is not released before any service is done on the hydraulic system. Make sure all of the attachments have been lowered to the ground, and the oil is cool before removing any components or lines. Remove the oil filler cap only when the engine is stopped, and the filler cap is cool enough to touch with your bare hand.

Note: Use the information in the reference to prepare the machine for this test. Also, use the information in the reference to relieve any hydraulic pressure that may be in the hydraulic system.

Reference: For the correct procedure to relieve any hydraulic oil pressure that may be in the hydraulic system, refer to Testing and Adjusting, "Machine Preparation for Troubleshooting" for your machine.

1. Warm the hydraulic oil to normal operating temperature. Normal operating temperature is 60° ± 10°C (140° ± 18°F).

2. After the oil has reached normal operating temperature, lower the grapple to the ground.

3. Stop the engine.

4. Relieve the hydraulic pressure. See the reference at the start of this procedure for the correct method.

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Illustration 1	g00638798
(1) Main implement pump. (2) Pressure tap for pump output.

5. Connect a 0 to 40000 kPa (0 to 5800 psi) pressure gauge to pressure tap (2). Pressure tap (2) for the pump output is located on main implement pump (1) .

   Note: Position the pressure gauge and the hydraulic lines in order to prevent damage from any moving components on the machine. Position the test equipment in order to allow either a second technician or the operator that is in the cab to observe the test equipment.

6. Start the engine.

7. Run the engine at high idle. High idle speed for this machine is 2350 ± 50 RPM.

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Illustration 2	g00638802
Hydraulic activation control lever in the UNLOCKED position (3) Hydraulic activation control lever. (4) Crossbar.

8. Shift hydraulic activation control lever (3) into the UNLOCKED position.

9. Actuate one of the stabilizer switches on the right control panel. actuate the function until the function is in a stalled state. While the function is stalled, record the pressure on the pressure gauge.

   Note: When either a tool group or stabilizer cylinder is activated, a solenoid is engaged. The solenoid allows oil flow to the load sensing relief valve for the delimber and the stabilizer. The load sensing relief valve for the delimber and the stabilizer is set to a lower pressure than the main relief valve. Therefore, the pump output pressure will be reduced.

10. The pressure that is recorded should be 20000 to 22500 kPa (2900 to 3265 psi).

    Note: If the pressure that is recorded is not within the specified pressure, the load sensing relief valve for the delimber and the stabilizer needs to be adjusted.

11. Lower the idle of the engine. Stop the engine.

12. Relieve the hydraulic pressure. See the reference at the start of this procedure for the correct method.

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Illustration 3	g00639632
(5) Load sensing relief valve for the delimber and the stabilizer. (6) Locknut. (7) Adjustment screw for the load sensing relief valve. (8) Solenoid. (9) Main control valve (three bank). (10) Main control valve (four bank).

13. Adjustment screw (7) is located behind main control valve (10) .

14. Loosen locknut (6) .

15. Make the proper changes to adjustment screw (7) .

16. Tighten locknut (6) .

17. Repeat steps 6 through 17 until the pump output pressure is correct.

18. Lower the idle of the engine. Stop the engine.

19. Relieve the hydraulic pressure. See the reference at the start of this procedure for the correct method.

20. Remove the hydraulic test lines and the pressure gauge.