Park the machine on a level surface. There must be sufficient overhead clearance so that the dump body can be fully raised. Move the parking brake control to the ENGAGED position and shut off the engine. Install the steering frame lock. Refer to Operation and Maintenance Manual, SEBU7028, "Steering Frame Lock".
Testing the Relief Pressure for the Hoist System
Testing the Relief Pressure (Raise)
- Install a pressure gauge on test fitting (1). The pressure gauge must be capable of measuring 34000 kPa (5000 psi).
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| Illustration 1 | g01045466 |
- Start the engine and run the engine at maximum speed.
- Move the hoist control to the RAISE position. When the body has reached full travel, hold the hoist control in the RAISE position and record the pressure that is displayed on the pressure gauge. This is the relief pressure (raise).
The relief pressure (raise) should be 20700 ± 340 kPa (3000 ± 50 psi). If the relief pressure (raise) is not 20700 ± 340 kPa (3000 ± 50 psi) the relief pressure (raise) must be adjusted.
- Lower the dump body and move the hoist control to the FLOAT position.
- Shut off the engine and remove the pressure gauge from the machine.
Testing the Relief Pressure (Lower)
- Install a pressure gauge on test fitting (2). The pressure gauge must be capable of measuring 21000 kPa (3000 psi).
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| Illustration 2 | g01045466 |
- Start the engine and run the engine at low idle.
- Move the hoist control to the LOWER position. When the body is in contact with the rear frame, hold the hoist control in the LOWER position and record the pressure that is displayed on the pressure gauge. This is the relief pressure (lower).
The relief pressure (lower) should be 6900 ± 340 kPa (1000 ± 50 psi). If the relief pressure (lower) is not 6900 ± 700 kPa (1000 ± 50 psi), the relief pressure (lower) must be adjusted.
- Move the hoist control to the FLOAT position.
- Shut off the engine and remove the pressure gauge from the machine.
Adjusting the Relief Pressure for the Hoist System
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Hot oil and hot components can cause personal injury. Do not allow hot oil or hot components to contact skin. |
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| NOTICE |
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Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting and repair of the product. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids. Refer to Special Publication, NENG2500, "Caterpillar Tools and Shop Products Guide" for tools and supplies suitable to collect and contain fluids on Caterpillar products. Dispose of all fluids according to local regulations and mandates. |
Lower the body. Move the hoist control to the FLOAT position and shut off the engine.
Note: If the relief pressure (raise) is adjusted, the relief pressure (lower) will be affected. The relief pressure (lower) must only be adjusted when the relief pressure (raise) is correct. The relief pressure (lower) may be adjusted independently of the relief pressure (raise).
Adjusting the Relief Pressure (Raise)
- Relieve the system pressure before you adjust the relief pressure for the hoist system. Refer to Systems Operation, Testing and Adjusting, "General Information".
- Loosen nut (3) and remove pipe (4) from elbow (5) .
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| Illustration 3 | g01045529 |
- Remove relief valve (6) from the hoist control valve.
- Secure the relief valve vertically with valve group (14) above valve group (13) .
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| Illustration 4 | g01045467 |
Components of relief valve (6) (7) Adapter (8) Shim pack (9) Shim pack (10) Spring (11) Piston (12) Valve (13) Valve group (14) Valve group (15) Retainer | |
- Remove valve group (14) from valve group (13) in order to access shim pack (9) .
Note: Ensure that you retain all of the components from the relief valve.
- If the relief pressure (raise) is below 20360 kPa (2950 psi), increase the thickness of shim pack (9). This will increase the relief pressure (raise). Refer to table 1.
If the relief pressure (raise) is above 21040 kPa (3050 psi), decrease the thickness of shim pack (9). This will decrease the relief pressure (raise). Refer to table 1.
Show/hide tableTable 1 Shims for the relief pressure for raising the body Pt. No. for Shim Thickness Approximate change in pressure 3J-7473 Shim
0.12 mm (0.005 inch)
700 kPa (100 psi)3H-2549 Shim
0.254 mm (0.0100 inch)
1470 kPa (210 psi)4T-4660 Shim
0.08 mm (0.003 inch)
460 kPa (67 psi)3J-7470 Shim
1.22 mm (0.048 inch)
7070 kPa (1030 psi)
- Reassemble the relief valve. Install valve group (14) into valve group (13). Install the relief valve into the hoist control valve and attach pipe (4) to elbow (5) with nut (3) .
Note: Ensure that valve (12) is properly seated before tightening any components.
- Refer to "Testing the Relief Pressure (Raise)" in order to test the new relief pressure (raise).
- Repeat steps 1 through 8 until the relief pressure (raise) is 20700 ± 340 kPa (3000 ± 50 psi).
Adjusting the Relief Pressure (Lower)
- Relieve the system pressure before you adjust the relief pressure for the hoist system. Refer to Systems Operation, Testing and Adjusting, "General Information".
- Loosen nut (3) and remove pipe (4) from elbow (5) .
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| Illustration 5 | g01045529 |
- Remove relief valve (6) from the hoist control valve.
- Secure the relief valve vertically with valve group (14) above valve group (13) .
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| Illustration 6 | g01045467 |
Components of relief valve (6) (7) Adapter (8) Shim pack (9) Shim pack (10) Spring (11) Piston (12) Valve (13) Valve group (14) Valve group (15) Retainer | |
- Remove adapter (7) from the relief valve in order to access shim pack (8) .
Note: Ensure that you retain all of the components from the relief valve.
- If the relief pressure (lower) is below 6560 kPa (950 psi), increase the thickness of shim pack (8). This will increase the relief pressure (lower). Refer to table 2.
If the relief pressure (lower) is above 7240 kPa (1050 psi), decrease the thickness of shim pack (8). This will decrease the relief pressure (lower). Refer to table 2.
Show/hide tableTable 2 Shims for the relief pressure for lowering the body Pt. No. for Shim Thickness Approximate change in pressure 4M-6978 Shim
0.508 mm (0.02 inch)
2950 kPa (430 psi)4M-6979 Shim
1.27 mm (0.05 inch)
7370 kPa (1070 psi)4M-6980 Shim
0.254 mm (0.01 inch)
1470 kPa (210 psi)4T-4659 Shim
0.8 mm (0.0315 inch)
4640 kPa (670 psi)
- Reassemble the relief valve. Install adapter (7) into valve group (14). Attach pipe (4) to elbow (5) with nut (3) .
Note: Ensure that valve (12) is properly seated before tightening any components.
- Refer to "Testing the Relief Pressure (Lower)" in order to test the new relief pressure (lower).
- Repeat steps 1 through 8 until the relief pressure (lower) is 6900 ± 340 kPa (1000 ± 50 psi).
- Remove the steering frame lock.