950G Series II Wheel Loader, 962G Series II Wheel Loader and IT62G Series II 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.

Illustration 1	g00834181
Location of the Pilot Valve (Oil Manifold) (1) Pressure tap. (2) Pressure reducing valve. (3) Secondary pressure reducing valve.

Illustration 2	g00298584
Location of the Loader Tower Access Panel

Note: The lift arms are raised for photographic purposes only.

Preparation for Testing

1. Park the machine on a smooth, level surface. Park the machine away from working machines and personnel. Lower the work tools to the ground.

2. Allow only one operator on the machine. Keep all personnel away from the machine or in the view of the operator.

3. Engage the parking brake.

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Illustration 3	g00914095

4. Place the steering frame lock in the LOCKED position.

   Reference: For more information about preparing the machine for troubleshooting, refer to the Service Manual module Testing and Adjusting, "Machine Preparation for Troubleshooting" for the machine that is being serviced.

Running Engine

1. Ensure that the work tool is on the ground. Turn the engine start switch to the OFF position.

2. 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.

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

4. Connect a gauge and hose from the 8T-5320 Hydraulic Test Group to the pressure tap (1) on the pilot manifold. Route the hose in order to clear the lift arms. Place the gauge in the cab. The pilot manifold is located in the rear section of the main hydraulic valve. Refer to Illustration 1 for the position of the pressure tap on the pilot manifold.

   Note: Access to the pressure tap (1) can be attained at the articulation hitch.

5. Start the engine and run the engine at high idle. Warm the hydraulic oil to a normal operating temperature of approximately 49° ± 3°C (120° ± 5°F).

6. Set the engine speed to low idle.

7. Measure the pilot pressure. Record the pilot pressure. Refer to Table 2 for the correct pressure.

8. If the pressure reading is correct, proceed to the Section "Stopped Engine with Raised Work Tool".

9. If the pressure reading is not correct, proceed to Step 10.

10. Ensure that the work tool is on the ground. Turn the engine start switch to the OFF position.

11. Release the hydraulic system pressure.

    Reference: For information about releasing the pressure in the hydraulic system, refer to the Service Manual module Testing and Adjusting, "System Pressure - Release" for the machine that is being serviced.

12. Ensure that the work tool is on the ground. Remove the loader tower access panel that is over the control valve in order to access the pressure reducing valve. Refer to Illustration 2 for the location of the loader tower access panel.

13. Replace 154-0191 Pressure Reducing Valve (2). Tighten the valve to the following torque 60 ± 7 N·m (45 ± 5 lb ft). If the 154-0191 Pressure Reducing Valve is adjusted then tighten the locking nut to the following torque 13 N·m (10 lb ft). In order to locate the reducing valve on the main control valve, refer to Illustration 1.

14. Repeat Step 5 through Step 7 in order to verify that the pilot pressure is correct.

15. In order to check the pilot pressure with a nonrunning engine, proceed to the Section "Stopped Engine with Raised Work Tool".

Stopped Engine with Raised Work Tool

1. Start the engine and run the engine at high idle. Warm the hydraulic oil to a normal operating temperature of approximately 49° ± 3°C (120° ± 5°F) .

2. Raise the work tool until the lift arms are fully extended. Turn the engine start switch to the OFF position.

3. Measure the pilot pressure. Record the pilot pressure. Refer to Table 2 for the correct pressure.

4. If the pressure reading is correct, proceed to Step 11.

5. If the pressure reading is not correct, proceed to Step 6.

6. Lower the work tool to the ground. Turn the engine start switch to the OFF position.

7. Release the hydraulic system pressure.

   Reference: For information about releasing the pressure in the hydraulic system, refer to the Service Manual module Testing and Adjusting, "System Pressure - Release" for the machine that is being serviced.

8. Ensure that the work tool is on the ground. Remove the loader tower access panel that is over the control valve in order to access the pressure reducing valve. Refer to Illustration 2 for the location of the loader tower access panel.

9. Replace the 154-8871 Secondary Pressure Reducing Valve (3). Tighten the valve to the following torque 60 ± 7 N·m (45 ± 5 lb ft). If the 154-8871 Pressure Reducing Valve is adjusted then tighten the locking nut to the following torque 13 N·m (10 lb ft). For the location of the reducing valve, refer to Illustration 1.

10. Repeat Step 1 through Step 3 in order to verify that the pilot pressure is correct.

11. Position the work tool on the ground. Turn the engine start switch to the OFF position. Remove the test equipment.

12. If the loader tower access panel must be removed, install the loader tower access panel.

13. Place the steering frame lock into the STORE position.