950G Wheel Loader, 962G Wheel Loader and IT62G Integrated Toolcarrier 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, 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.

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Sudden movement or accidental starting of the machine can cause personal injury or death to persons on or near the machine. To prevent personal injury or death, perform the following: Park the machine on a smooth, level surface. Lower the work tool to the ground and engage the parking brake. Stop the engine and remove the key. Block the wheels and install the steering frame lock.

Note: This test procedure describes the line relief valves for the tilt cylinders. Line relief valves for the auxiliary cylinders can be tested by using the same basic procedure.

Illustration 1	g00500589
View of the Control Levers and the Fourth Function Switch (1) Tilt lever (2) Lift lever (3) Auxiliary lever (4) Fourth function switch

In order to test the relief valves for the third function, install the pressure gauge on the pressure taps for the third function. Use auxiliary lever (3) to operate the cylinders for the third function.

In order to test the relief valves for the fourth function, fourth function switch (4) must be actuated. Tilt control lever (1) will then control the auxiliary cylinders for the fourth function. You must also install the pressure gauge on the pressure taps for the fourth function.

Illustration 2	g00500590
Location of Both Main Control Valves (5) Main control valve (tilt and auxiliary) (6) Main control valve (lift and auxiliary)

1. Start the engine. Run the engine at high idle. Operate the control levers and move all the cylinders in order to increase the temperature of the hydraulic oil to normal operating temperature.

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Illustration 3	g00500591
Main Control Valve (Tilt and Auxiliary) (7) Main relief valve (8) Relief valve for tilt cylinders (rod end) (9) Relief valve for tilt cylinders (head end) (10) Relief valve for auxiliary cylinder (third function) (11) Relief valve for auxiliary cylinder (third function)

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Illustration 4	g00501440
Main Control Valve (Lift and Auxiliary) (12) Auxiliary relief valves (fourth function).

2. Lower the bucket to the ground or onto jack stands. Remove the cover that is over the main control in order to access the main relief valve and the line relief valves.

3. Stop the engine.

4. Move the control levers through the full range of travel several times. This will relieve any pressure that may be present in the implement hydraulic system.

5. Push on the hydraulic tank breaker relief valve in order to relieve the pressure in the hydraulic oil tank. Push in the plunger until all pressure is released from the hydraulic oil tank.

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Illustration 5	g00500587
(13) Rod end of tilt cylinders (14) Head end of tilt cylinders (15) Fourth function (16) Fourth function (17) Third function (close/lower) (18) Third function (open/raise)

6. Connect 1U-5481 Pressure Gauge Group on the proper pressure tap.

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Illustration 6	g00500594
Main Relief Valve (19) Locknut (20) Adjustment screw (21) Cap

Note: The main relief valve has a lower setting than some line relief valves. To correctly set some line relief valves, the main relief valve setting must be temporarily increased. In order to increase the pressure setting for the main relief valves, follow Steps 7 through 9.

7. Remove cap (21) .

8. Loosen locknut (19) .

9. Turn adjusting screw (20) clockwise in order to increase the pressure setting.

10. Start the engine. Run the engine at low idle.

11. Raise the bucket so that the lift arms are parallel to the ground.

    Note: In the following steps, do not keep the tilt control lever in the TILT BACK position or the DUMP position for more than five seconds while the pressure is at the relief valve setting.

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    Table 2

    Line Relief Valves
    Relief Valve	IT62G
    Tilt (rod end)	24800 ± 400 kPa (3600 ± 60 psi)
    Tilt (head end)	20000 ± 400 kPa (2900 ± 60 psi)
    Auxiliary rod end (third function)	22750 ± 400 kPa (3300 ± 60 psi)
    Auxiliary head end (third function)	22750 ± 400 kPa (3300 ± 60 psi)
    Auxiliary rod end (fourth function)	20700 ± 400 kPa (3000 ± 60 psi)
    Auxiliary head end (fourth function)	20700 ± 400 kPa (3000 ± 60 psi)

12. Test for the Line Relief Valve (Head End). Move the bucket to the full TILT BACK position. Move and then hold the tilt control lever to the TILT BACK position. Observe the pressure gauge. The high reading on the pressure gauge is the pressure setting of the line relief valve.

13. Test for the Line Relief Valve (Rod End). Move the bucket to the full DUMP position. Move the tilt control lever in the DUMP position and observe the pressure gauge. The high reading on the pressure gauge is the pressure setting of the line relief valve.

    If the pressure setting of the line relief valve is not at the specification, it will be necessary to adjust the line relief valve. Proceed to Step 14.

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Illustration 7	g00501460
Line Relief Valve on the Main Control Valve (Tilt and Auxiliary) (22) Locknut (23) Adjustment screw (24) Cap

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Illustration 8	g00501461
Line Relief Valve on the Main Control Valve (Lift and Auxiliary) (25) Locknut (26) Adjustment screw

14. Stop the engine.

    Note: The relief valve in Illustration 7 is used on the main control valve (tilt and auxiliary). The line relief valves for the main control valve (lift and auxiliary) are slightly different but the same basic adjustment procedures are used. Some valves are adjusted with a flat head screwdriver while some valves require an allen wrench.

    Use the following procedure in order to adjust the line relief valve on the main control valve (tilt and auxiliary). Step 15 describes the procedure to adjust the line relief valves for the main control valve (tilt and auxiliary).

    1. Remove cap (24). Loosen locknut (22) and turn adjusting screw (23) clockwise in order to increase the relief valve setting. Turn adjusting screw (23) counterclockwise in order to decrease the relief valve setting.

    2. After adjusting screw (23) is turned for an adjustment, tighten locknut (22) to a torque of 65 ± 5 N·m (48 ± 4 lb ft).

15. The following procedure is used in order to adjust the line relief valve on the main control valve (lift and auxiliary).

    1. Loosen locknut (25) and turn adjusting screw (26) clockwise in order to increase the relief valve setting. Turn adjusting screw (26) counterclockwise in order to decrease the relief valve setting.

       After adjusting screw (26) is turned for an adjustment, tighten locknut (25) to a torque of 50 ± 7 N·m (37 ± 5 lb ft).

16. Repeat Steps 10 through 13.
    • If the pressure setting is not correct, repeat Step 14.

    • If the pressure setting is correct, stop the engine and remove the test equipment.

17. In order to test the next pressure tap, return to Step 6. Once the head end and the rod end of each line relief valve has been checked, proceed to Step 18.

18. Reset the main relief valve.

Reference: For information on resetting the main relief valve, refer to the Service Manual module for Testing and Adjusting, "Relief Valve (Main) - Test and Adjust".