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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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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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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, "Dealer Service Tool Catalog" for tools and supplies suitable to collect and contain fluids on Cat products. Dispose of all fluids according to local regulations and mandates. |
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| Illustration 1 | g02701918 |
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(1) Relief valve for center pump
(2) Relief valve for right pump (3) Relief valve for left (front) pump (4) Relief valve for left (rear) pump | |
Reference: For the pressure and flow for bench testing this valve, refer to the Service Manual module Specifications, "Piston Pump (Implement, Variable Displacement)" for the machine that is being serviced.
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The line relief is set higher than the main relief. Do not increase the main relief setting to check the line relief setting. Damage to the hydraulic system may result. |
- Connect Caterpillar ET to the machine. The ET connector is located on the control panel on the right side of the cab.
- Turn the engine start switch to the ON position.
- Open the ET software program.
- When ET has started, start the engine. Run the engine at high idle. Warm the hydraulic oil to normal operating temperature.
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Illustration 2 g02635537 Typical example - Select "Implement 994H". Press the "OK" button.
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Illustration 3 g02619025 Typical example - Select "Diagnostic Tests" from the "Diagnostics" menu.
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Illustration 4 g02619056 Typical example - Select "Implement Main Relief Pressure Tests".
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Illustration 5 g02619081 Typical example - When the dialog box appears on the screen, read the information in the dialog box. In order to continue with the test procedure, select the "OK" button.
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Illustration 6 g02619087 Typical example - When the dialog box appears on the screen, four checked boxes appear. Leave the check mark in the box for each test that will be performed. Select the "Begin" button in order to start the procedure.
- Press the "Next" button in order to begin the procedure. Follow the instructions on the screen. A check mark will appear next to each step as each step is completed.
- Make sure that the area around the machine is level and clear of obstacles. Keep all personnel away from the machine. Press the "Next" button.
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Illustration 7 g02619096 Typical example - Engage the parking brake.
- Place the hydraulic lockout switch in the UNLOCKED position.
- Warm the hydraulic oil to a temperature to between
60° C (140° F) and65° C (149° F) .Show/hide table
Illustration 8 g02619280 Typical example - Raise the bucket fully. Press the "Next" button.
- Rack the bucket fully. Press the "Next" button.
- Ensure that the engine is set and the throttle is locked at high idle.
- Ensure that the levers are in the HOLD position. Press the "Next" button.
- Pull the lift lever fully into the full RAISE position and hold that position.
- Release the lift lever to the HOLD position. Press the "Next" button.
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Illustration 9 g02631119 Typical example - If the measured pressure was within the specification, ET will proceed to Step 23. If the pressure was not within the specification, proceed to the next step.
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Illustration 10 g02631229 Typical example - A dialog box will appear. The box will indicate that the measured pressure is not within the specification. Adjust the main relief valve. Follow the instructions in the dialog box. After adjusting the valve, press the "OK" button. ET will return to Step 12.
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Illustration 11 g02631236 - When the procedure is complete, the "Service Test Successful" message will appear on the screen. In order to exit the program, select the "Finish" button.
- Repeat Step 1 through Step23 for the remaining main relief valves for the piston pumps.
- Turn the engine start switch to the OFF position. Disconnect ET from the machine.
