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. Release all hydraulic system pressure.

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Illustration 1	g00639550
(1) Main pressure relief valve. (2) Main control valve (three bank). (3) Locknut for the main pressure relief valve. (4) Adjustment screw for the main pressure relief valve. (5) Main control valve (four bank).

2. Loosen locknut (3) for the main pressure relief valve.

3. Turn adjustment screw (4) clockwise by one complete turn. This will allow the line relief valves to actuate before main pressure relief valve (1). Main pressure relief valve (1) is located on main control valve (2). Main control valve (2) is located under the third step of the upper body.

4. Tighten locknut (3) .

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Illustration 2	g00639581
(5) Main control valve (four bank). (6) Connector. (7) Solenoid.

5. Disconnect connector (6). Solenoid (7) will not function while connector (6) is disconnected. When solenoid (7) is activated oil flows to the relief valve for the delimber and stabilizer control valve. The relief valve (delimber and stabilizer) must be disconnected in order to allow the line relief valves for the tool groups to relieve pressure.

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Illustration 3	g00639586
(8) Main implement pump. (9) Pressure tap for pump output.

6. Connect a 0 to 60000 kPa (0 to 8700 psi) pressure gauge to pressure tap (9). Pressure tap (9) is located on main implement pump (8) .

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NOTICE
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.

7. Start the engine.

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

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

10. Shift the hydraulic lever lock to the UNLOCKED position.

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NOTICE
Do not hold this function or any other function stalled for more than 10 seconds. Hydraulic oil is heated very rapidly when the oil is channeled through relief valves. Component damage could result.

11. Actuate the boom upward until the boom is in a stalled state. Record the pressure on the pressure gauge while the function is stalled.

12. The recorded pressure should be 38000 to 40000 kPa (5500 to 5800 psi).

    Note: If the pressure reading is not within specifications, the line relief valve for the boom function needs to be adjusted. Follow steps 14 through 20 in order to adjust the line relief valve for the boom function.

13. Continue to test each function's line relief valve. The pressure for each line relief valve must be taken while the corresponding function is stalled. Apply steps 11 and 12 in order to test each function's line relief valve. Table (2) has specifications for each line pressure that should be tested.
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    Table 2

    Line Relief Valve Pressures
    Function	Pressure
    Boom Up	38000 - 40000 kPa 5500 - 5800 psi
    Boom Down	38000 - 40000 kPa 5500 - 5800 psi
    Stick In	38000 - 40000 kPa 5500 - 5800 psi
    Stick Out	38000 - 40000 kPa 5500 - 5800 psi
    Grapple Open	38000 - 40000 kPa 5500 - 5800 psi
    Grapple Close	38000 - 40000 kPa 5500 - 5800 psi
    Grapple Rotate (clockwise direction)	21000 - 23000 kPa 3050 - 3350 psi
    Grapple Rotate (counterclockwise direction)	21000 - 23000 kPa 3050 - 3350 psi
    Tool Section (three bank - LH stabilizers)	26000 - 28000 kPa 3770 - 4060 psi
    Tool Section (four bank - RH stabilizers)	26000 - 28000 kPa 3770 - 4060 psi

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Illustration 4	g00639603
(10) Tool section (Not active). (11) Grapple rotate clockwise. (12) Swing (plug). (13) Tool section (Not active). (14) Grapple open. (15) Stick in. (16) Boom down. (17) Tool section. (18) Grapple rotate counterclockwise. (19) Swing (plug). (20) Tool section. (21) Grapple close. (22) Stick out. (23) Boom up. (A) Front of the machine. (B) Back of the machine.

Note: The ports for swing (12) and swing (19) contain plugs. Line relief valves for the swing are located on the swing motor. A separate test is used to check the swing relief valves.

14. In order to adjust the line relief valve, locate the adjustment screw for the line relief valve that corresponds to the function that is being tested.

15. Stop the engine.

16. Release all hydraulic system pressure. See the reference at the start of this procedure for the correct method.

17. Loosen the locknut for the line relief valve.

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NOTICE
Use extreme caution when adjusting relief valves. A small turn to the adjustment screw can cause a great amount of change to the pressure cutoff. Setting the relief pressure too high can result in component failure.

18. Make the proper adjustment to the adjustment screw for the line relief valve. One quarter turn of the adjustment screw in a clockwise direction will raise the cutoff pressure by 1000 kPa (145 psi).

19. Tighten the locknut for the line relief valve.

20. Repeat step 13 in order to check the pressure of the adjusted line relief valve.

21. Lower the engine idle. Stop the engine.

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

23. Remove the hydraulic test equipment and pressure gauges.

24. Loosen locknut (3) for the main pressure relief valve.

25. Turn the adjustment screw for the main pressure relief valve counterclockwise by one complete turn. The adjustment screw should be back to the original position.

26. Tighten locknut (3) .

27. Join connector (6). Solenoid (7) will be active.