993K Wheel Loader Electrohydraulic System Caterpillar

The main relief valve pressure test determines if the main relief valves are set to the correct relief pressure.

1. Start the engine. Warm the hydraulic oil to a normal operating temperature of 68° ± 20°C (154° ± 36°F).
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   Illustration 1	g01445414

2. Select "Service" from the "Home Menu" on the Advisor display.
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   Illustration 2	g01445436

3. Select "Service Modes" from the "Service" menu on the Advisor display.
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   Illustration 3	g01445450

4. Select "Implement" from the "Service Modes" menu on the Advisor display.
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   Illustration 4	g01445455

5. Select "Main Relief Pres Check" from the "Implement" menu on the Advisor display.

6. Follow the steps on the screen in order to test the pressure setting for the main relief valves.

7. The correct pressure setting for each main relief valve should be 29500 ± 340 kPa (4300 ± 50 psi).

Adjusting the Main Relief Valves

If the test indicates that either of the main relief valves needs to be adjusted, use the following procedure in order to adjust the valves.

1. Stop the engine.

2. Connect the steering frame lock.

3. Shift the transmission to the NEUTRAL position. Engage the parking brake.
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   Illustration 5	g01445527
   Main control valve (right) (front view) (1) Main relief valve

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   Illustration 6	g01445531
   Main control valve (left) (front view) (2) Main relief valve

4. Locate the correct main relief valve. Refer to Illustration 5 or Illustration 6.

5. Loosen the locknut on the relief valve.

6. Turn the adjustment screw clockwise in order to increase the pressure setting. Turn the adjustment screw counterclockwise in order to decrease the pressure setting.

   Note: One turn of the adjustment screw will change the pressure setting by 5100 kPa (750 psi).

   Note: When you adjust a relief valve, start the adjustment at a set point below the specified relief pressure. Adjust the pressure up to the specified pressure setting for the relief valve.

7. Tighten the locknut on the valve.

8. Repeat the test in order to ensure that the new setting is correct.