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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. |
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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. |
| NOTICE |
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For all relief valve tests, the recommended method to test a relief valve is to remove the valve fom the machine and use a test bench to test and adjust the valve. |
| Required Tools | ||
| Part Number | Description | Qty |
| 1U-5481 | Pressure Gauge Group | 1 |
| 1U-5482 | Pressure Adapter Group | 1 |
| 8S-7630 (1) | Stand | 2 |
| 8S-7641 | Tube | 2 |
| 8S-8048 | Saddle | 2 |
| 8S-7615 | Pin | 2 |
| ( 1 ) | Optional tooling |
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| Illustration 1 | g00499829 |
Main Control Valve (Tilt and Auxiliary) (1) Main relief valve. | |
- 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.
- Lower the bucket to the ground. Remove the cover that is over the control valve in order to access the main relief valve and the line relief valves.
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| Illustration 2 | g00499835 |
Front View without Access Panel | |
- Stop the engine.
Note: To improve access to the relief valves, rest the lift arms or the attachments on a jack stand.
- 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.
- Push on breaker relief valve (2) in order to relieve the pressure in the hydraulic tank. Push in the plunger until all pressure is released from the hydraulic oil tank.
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| Illustration 3 | g00499779 |
Location of Hydraulic Oil Tank and the Relief Valve Plunger (2) Breaker relief valve. | |
- Connect 1U-5481 Pressure Gauge Group on pressure tap (3) .
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| Illustration 4 | g00499827 |
Articulation Joint (Left Side) (3) Pressure tap for main implement pressure. | |
- Start the engine. Raise the bucket to the maximum height.
- Increase the engine speed to high idle. Observe the pressure gauge and move the lift control lever to the RAISE position.
Note: The proper pressure setting for the main relief valve is 20700 ± 350 kPa (3000 ± 50 psi). If the pressure setting of the main relief valve is not at the specification, it will be necessary to adjust the main relief valve.
- Stop the engine.
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Illustration 5 g00499768
Sectional View of the Main Relief Valve
(4) Locknut
(5) Adjustment screw
(6) Cap
- Loosen locknut (4) and turn adjusting screw (5) clockwise in order to increase the relief valve setting. Turn adjusting screw (5) counterclockwise in order to decrease the relief valve setting.
- After adjusting screw (5) is turned for an adjustment, tighten locknut (4) to a torque of 65 ± 5 N·m (48 ± 4 lb ft).
- Repeat Steps 7 and 8.
Note: In the following steps, do not keep the lift control lever in the RAISE position for more than five seconds while the pressure is at the relief setting.
- If the pressure setting is not correct, repeat Steps 8.a through 8.d.
- If the pressure setting is correct, stop the engine and lower the bucket to the ground.
- Reinstall the loader tower access panel on the machine. Remove the test equipment.