AD45B Underground Articulated Truck Hydraulic System Caterpillar

Dump Body Machines

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Personal injury or death can result from sudden machine movement. Sudden movement of the machine or release of oil pressure can cause injury to persons on or near the machine. To help prevent possible injury or death, refer to the information in Testing and Adjusting, "Machine Preparation for Troubleshooting".

Note: Make sure that the filters and the screens are clean before you test any pressures. Make sure that the oil is at operating temperature before you perform this test.

Note: Before you perform any tests, visually inspect the entire hydraulic system for oil leaks and for damaged components.

Illustration 1	g01043845
(1) High pressure relief valve (2) Low pressure relief valve (3) Hoist dual stage relief valve (4) Hoist control valve

Hoist dual stage relief valve (3) is part of the hoist control valve (4). The relief pressure for the RAISE position is controlled by high pressure relief valve (1). The relief pressure for the LOWER position is controlled by low pressure relief valve (2) .

Relief Valve Test (High Pressure)

1. Lower the dump body. Stop the engine.

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Illustration 2	g01190715
Manifold for the hoist cylinder lines (5) Pressure tap

2. Remove the protective cover from the pressure tap (5). Connect a hose assembly with an 8T-0860 Pressure Gauge (0 to 40000 kPa (0 to 5800 psi)) to pressure tap (5) .

3. Start the engine. Operate the dump body repeatedly until the temperature of the hydraulic oil is above 38°C (100°F).

4. Run the engine at high idle and move the hoist control to the RAISE position.

5. After the dump body is fully raised, look at the gauge and hold the hoist control in the RAISE position. The pressure gauge reading is the relief valve pressure setting of high pressure relief valve (1). The correct pressure setting is 18270 + 1035 - 0 kPa (2650 + 150 - 0 psi).

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Illustration 3	g00531382
(1) High pressure relief valve (2) Low pressure relief valve (3) Hoist dual stage relief valve (6) Nut (7) Retainer

6. If the pressure reading is not correct, loosen nut (6). Turn retainer (7) in order to adjust the setting of high pressure relief valve (1). Turn retainer (7) clockwise in order to increase the pressure setting and turn retainer (7) counterclockwise in order to decrease the pressure setting.

7. When high pressure relief valve (1) is correctly set, tighten nut (6) .

8. Lower the dump body and stop the engine.

9. Remove the test equipment. Place the protective cover on the pressure tap.

Relief Valve Test (Low Pressure)

1. Lower the dump body. Stop the engine.

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Illustration 4	g00854724
Manifold for the hoist cylinder lines (8) Pressure tap

2. Remove the protective cover from pressure tap (8). Connect a hose assembly with an 8T-0856 Pressure Gauge (0 to 6000 kPa (0 to 870 psi)) to pressure tap (8) .

3. Start the engine. Operate the dump body repeatedly until the temperature of the hydraulic oil is above 38°C (100°F).

4. Lower the dump body on the truck frame.

   Note: The body position sensor must be in the RAISE position before low pressure relief valve (2) can be measured. If the body position sensor is in the LOWER position, the Power Train/Chassis Electronic Control Module will keep the hoist control valve in the SNUB position. Low pressure relief valve (2) can not be measured in this position.

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Illustration 5	g00854726
Body position sensor secured in the RAISE position (9) Body position sensor

5. Disconnect the return spring from the lever on body position sensor (9). Rotate the lever on the body position sensor to the RAISE position. Secure the lever in this position, as shown.

6. Move the hoist control to the HOLD position. Run the engine at high idle and move the hoist control to the LOWER position.

7. Look at the gauge and hold the hoist control in the LOWER position. The pressure gauge reading is the relief valve pressure setting of low pressure relief valve (2). The correct pressure setting is 3450 ± 350 kPa (500 ± 50 psi).

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Illustration 6	g00854780
(1) High pressure relief valve (2) Low pressure relief valve (3) Hoist dual stage relief valve (10) Retainer (11) Nut

8. If the pressure reading is not correct, loosen nut (11). Turn retainer (10) in order to adjust the setting of low pressure relief valve (2). Turn retainer (10) clockwise in order to increase the pressure setting, and turn retainer (10) counterclockwise in order to decrease the pressure setting.

9. When low pressure relief valve (2) is correctly set, tighten nut (11) .

10. Stop the engine. Reposition the lever on the body position sensor against the support in the LOWER position. Connect the return spring to the lever on the body position sensor.

11. Remove the test equipment. Place the protective cover on the pressure tap.

Ejector Body Machines

Illustration 7	g01043845
(1) Eject relief valve (2) Retract relief valve (3) Hoist dual stage relief valve (4) Hoist control valve

Hoist dual stage relief valve (3) is part of the hoist control valve (4). The relief pressure for the EJECT position is controlled by eject relief valve (1). The relief pressure for the RETRACT position is controlled by retract relief valve (2) .

Relief Valve Test (Eject)

1. Stop the engine.

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Illustration 8	g00854722
Manifold for the ejector cylinder lines. (5) Pressure tap

2. Remove the protective cover from the pressure tap (5). Connect a hose assembly with an 8T-0860 Pressure Gauge (0 to 40000 kPa (0 to 5800 psi)) to pressure tap (5) .

3. Start the engine. Operate the ejector system repeatedly until the temperature of the hydraulic oil is above 38°C (100°F).

4. Run the engine at high idle and move the hoist control to the EJECT position.

5. After the ejector plate is fully ejected, look at the gauge and hold the hoist control in the EJECT position. The pressure gauge reading is the relief valve pressure setting of eject relief valve (1). The correct pressure setting is 15858 + 1035 - 0 kPa (2300 + 150 - 0 psi).

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Illustration 9	g00531382
(1) Eject relief valve (2) Retract relief valve (3) Hoist dual stage relief valve (6) Nut (7) Retainer

6. If the pressure reading is not correct, loosen nut (6). Turn retainer (7) in order to adjust the setting of eject relief valve (1). Turn retainer (7) clockwise in order to increase the pressure setting and turn retainer (7) counterclockwise in order to decrease the pressure setting.

7. When eject relief valve (1) is correctly set, tighten nut (6) .

8. Retract the ejector plate. Stop the engine.

9. Remove the test equipment. Place the protective cover on the pressure tap.

Relief Valve Test (Retract)

1. Stop the engine.

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Illustration 10	g00854724
Manifold for the ejector cylinder lines. (8) Pressure tap

2. Remove the protective cover from the pressure tap (8). Connect a hose assembly with an 8T-0860 Pressure Gauge (0 to 40000 kPa (0 to 5800 psi)) to pressure tap (8) .

3. Start the engine. Operate the ejector system repeatedly until the temperature of the hydraulic oil is above 38°C (100°F).

4. Run the engine at high idle and move the hoist control to the RETRACT position.

5. After the ejector plate is fully retracted, look at the gauge and hold the hoist control in the RETRACT position. The pressure gauge reading is the relief valve pressure setting of retract relief valve (2). The correct pressure setting is 15858 + 1035 - 0 kPa (2300 + 150 - 0 psi).

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Illustration 11	g01190254
(1) Eject relief valve (2) Retract relief valve (3) Hoist dual stage relief valve (9) Retainer (10) Nut

6. If the pressure reading is not correct, loosen nut (10). Turn retainer (9) in order to adjust the setting of retract relief valve (2). Turn retainer (9) clockwise in order to increase the pressure setting, and turn retainer (9) counterclockwise in order to decrease the pressure setting.

7. When retract relief valve (2) is correctly set, tighten nut (10) .

8. Stop the engine.

9. Remove the test equipment. Place the protective cover on the pressure tap.