R2900G Load Haul Dump 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 work tools 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.

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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.

Testing Line Relief Valve - Rod End

Illustration 1	g01037448
(1) Main relief valve (2) Main control valve (3) Line relief valve for the head end of the tilt cylinder (4) Line relief valve for the rod end of the tilt cylinder

1. Start the engine and increase the temperature of the hydraulic oil to normal operating temperature.

2. Stop the engine.

3. Release the pressure from the hydraulic system.

   Reference: Refer to Systems Operation, Testing and Adjusting, "System Pressure - Release" in this manual.

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   Illustration 2	g01896355
   (5) Pressure tap for the rod end of the tilt cylinder

4. Connect an 8T-0858 Pressure Gauge to pressure tap (5).

5. Start the engine. Raise the lift arms so that the bucket will clear the ground in the full DUMP position.

6. Apply the service brake and disengage the parking brake.

7. Operate the engine at low idle rpm.

8. Raise the lift arms to maximum height with the bucket in the full Dump position. Record the pressure reading from the pressure gauge that is connected to pressure tap (5).If the pressure reading does not agree with the value in Table 2, proceed to "Adjusting the Line Relief Valve".

   If the pressure reading agrees with the value in Table 2, proceed to Step 9.

9. Engage the parking brake and stop the engine.

10. Release the hydraulic system pressure.

    Reference: Refer to Systems Operation, Testing and Adjusting, "System Pressure - Release" in this manual.

11. Remove the test equipment.

Testing Line Relief Valve - Head End

Illustration 3	g01037448
(1) Main relief valve (2) Main control valve (3) Line relief valve for the head end of the tilt cylinder (4) Line relief valve for the rod end of the tilt cylinder

1. Start the engine and increase the temperature of the hydraulic oil to normal operating temperature.

2. Stop the engine.

3. Release the pressure from the hydraulic system.

   Reference: Refer to Systems Operation, Testing and Adjusting, "System Pressure - Release" in this manual.

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   Illustration 4	g01894794
   (6) Pressure tap for the head end of the tilt cylinder

4. Connect an 8T-0860 Pressure Gauge to pressure tap (6).

5. Start the engine. Operate the engine at low idle rpm.

6. Raise the lift arms to maximum height, and move the bucket to the full tilt back position.

   Note: Do not hold the joystick control lever in the TILT BACK position for more than 5 seconds while the pressure is at the relief setting. Minimize these conditions to avoid the rapid heating of the hydraulic oil.

7. Lower the lift arms until the bucket stops contact with the lift arms. Record the pressure reading from the pressure gauge that is connected to pressure tap (6).

   If the pressure reading does not agree with the value in Table 4, proceed to "Adjusting the Line Relief Valve".

   If the pressure reading agrees with the value in Table 4, proceed to Step 8.

8. Set the main relief valve to the pressure in Table 3.

   Reference: For additional information on setting the main relief valve, refer to Systems Operation, Testing and Adjusting, "Relief Valve (Main) - Test and Adjust" in this manual.

9. Stop the engine.

10. Release the hydraulic system pressure.

    Reference: Refer to Systems Operation, Testing and Adjusting, "System Pressure - Release" in this manual.

11. Remove the test equipment.

Adjusting the Line Relief Valve

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Illustration 5	g01037456
Line relief valve (7) Adjusting screw (8) Locknut

1. Refer to Illustration 3 for the location of the line relief valves.

2. Loosen locknut (8). Turn adjusting screw (7) clockwise to increase the relief valve setting.

3. Turn adjusting screw (7) counterclockwise to decrease the relief valve setting.

4. After adjusting screw (7) is turned for an adjustment, tighten locknut (8) to a torque of 50 ± 7 N·m (37 ± 5 lb ft).

5. Test the rod end line relief valve pressure. Refer to "Testing Line Relief Valve - Rod End".

6. Test the head end line relief valve pressure. Refer to "Testing Line Relief Valve - Head End".