422E, 428E, 432E, 434E, 442E and 444E Backhoe Loaders Hydraulic and Steering System Hydraulic Pump - Test and Adjust Caterpillar

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Sudden movement of the machine or release of oil under pressure can cause serious injury to persons on or near the machine. To prevent possible injury, perform the procedure that follows before testing and adjusting the hydraulic system.

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Personal injury or death can result from escaping fluid under pressure. Escaping fluid under pressure, even a very small pin-hole size leak, can penetrate body tissue and cause serious injury and possible death. If fluid is injected into your skin, it must be treated immediately by a doctor familiar with this type of injury. Always use a board or cardboard when checking for a leak.

Illustration 1	g02177312
(1) Hydraulic pump (2) Flow compensator valve (3) Pressure compensator valve (4) Signal pressure tap

Note: Do not adjust the pressure compensator (3). Any attempt to tamper with the pressure compensator could result in a valve and a pump failure.

Signal pressure tap (4) is located on hydraulic pump (1). Flow compensator valve (2) and pressure compensator valve (3) are also located on hydraulic pump (1). Access is gained from the bottom of the machine or access is gained by removing the floorplate.

Illustration 2	g02177315
(1) Hydraulic pump (5) System pressure tap

System pressure tap (5) is located at the bottom of pump (1). Access is gained from the bottom of the machine.

Prior to making any pump adjustments, perform "Low Pressure Standby Pressure Test", "Margin Pressure Test" and "High Pressure Stall Test".

Increase the hydraulic oil temperature to the operating temperature by installing the boom lock, setting the engine to HI IDLE, and stalling the boom down for 60 seconds. Check for leaks.

Assembly of the Hose Assemblies

1. Install one 6V-4143 Coupler to each end of the 177-7860 Hose Assemblies .

2. Install one 6V-3989 Fitting to each pressure gauge.

Low Pressure Standby Pressure Test

1. Start the engine.

2. Lower the work tool on the front of the machine and the stabilizers to the ground. Engage the parking brake. Stop the engine.

3. Move the hydraulic hand controls to all the positions in order to release system pressure.

4. Remove the floorplate and the floor mat.
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   Illustration 3	g00869466

   1. Remove two bolts (6) and plate (7) .
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   Illustration 4	g00869467

   2. Remove two bolts (8) and plate (9). Remove floor mat (10) .
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   Illustration 5	g00869469

   3. Remove six bolts (11) from the perimeter of floorplate (12). Set floorplate (12) aside.

5. Install the 8T-0856 Pressure Gauges with a range of 0 to 6000 kPa (0 to 870 psi) to each hose assembly. Install one hose assembly to pressure tap (5) for system pressure. Install one hose assembly to signal pressure tap (4). Refer to Illustration 1 and Illustration 2.

6. Start the engine. Run the engine at HIGH idle. Check for leaks.

   Note: Do not move any hydraulic hand controls nor move the steering wheel while the 8T-0856 Pressure Gauges are installed. The higher pressure that is created by upstroking the pump will damage the gauges.

7. Lower the engine speed to 1200 RPM.

8. The pressure reading on the gauge that is attached to signal pressure tap (4) should be approximately 500 kPa to 1500 kPa (70 psi to 218 psi). This pressure is the standby signal pressure. The standby signal pressure is not adjustable. If the standby signal pressure is in the range, proceed to Step 10.

   Note: The standby signal pressure will vary with each machine.

9. If the standby signal pressure is out of the range, remove the test equipment and cycle the steering. Then, perform the test again. If the standby signal pressure is out of the range, there is a possibility of a plugged orifice in the priority spool or in the metering pump.

10. Do not move any hydraulic hand controls nor move the steering wheel. The pressure reading on the gauge that is attached to pressure tap (5) is the low standby discharge pressure. The low standby discharge pressure should be approximately 2000 kPa to 3600 kPa (290 psi to 522 psi).

    Note: If the standby discharge pressure is not correct perform the "Margin Pressure Test".

11. Stop the engine.

12. Move the hydraulic hand controls to all the positions in order to release system pressure.

13. Remove all test equipment.

    Note: Failure to remove the 8T-0856 Pressure Gauges prior to performing the following tests will cause the gauges to be destroyed, when the pump is upstroked. A 1U-5793 Pressure Differential Gauge should be used in order to perform the "Margin Pressure Test".

Margin Pressure Test

1. A 1U-5793 Pressure Differential Gauge is used in order to perform the margin pressure test. Attach one 177-7860 Hose As to pressure tap (5) for the pump discharge pressure. Attach the other end of the hose assembly to the 1U-5793 Pressure Differential Gauge. Install the other 177-7860 Hose As to signal pressure tap (4). Connect the other end of the hose assembly to the 1U-5793 Pressure Differential Gauge .

2. Engage the parking brake. Start the engine. Keep the machine in NEUTRAL.

3. Run the engine at 1200 RPM.

4. Turn the steering to the stops in both directions for three cycles. Turn the steering to the right to the stop.

   Note: There may be air in the signal network, if there is a hesitation before reaching the relief pressure. Purge the signal lines of the air.

5. Read the pressure on the differential pressure gauge. This is the margin pressure. The margin pressure should be 2200 kPa to 2900 kPa (319 psi to 421 psi). If the margin pressure is out of the specification, then refer to "Flow Compensator Spool Adjustment" in "Adjustments for the Pump Controller".

6. Return the steering wheel to the centered position.

7. In order to verify the pressure, repeat Step 4 and Step 5.

8. Run the engine at LOW idle. Stop the engine.

   Note: Do not make adjustments to the pressure compensator spool.

9. If the margin pressure is correct, proceed to the "High Pressure Stall Test".

High Pressure Stall Test

High Pressure Stall Test for the Backhoe

1. Remove the 1U-5793 Pressure Differential Gauge that was used in the "Margin Pressure Test". Connect a 8T-0860 Pressure Gauge with a range of 0 to 40000 kPa (0 to 5800 psi) to the hose assembly that is connected to pressure tap (5) .

2. Install the swing lock pin and install the boom lock.

3. Ensure that the work tool on the front of the machine and the stabilizers are on the ground. Engage the parking brake.

4. Start the engine. Run the engine at 1200 RPM.

5. Move the boom control to the RAISED position and the bucket into the DUMP position in order to initiate a stall condition for the boom. Note the pressure reading at pressure tap (5) .

6. See Table 2 for the proper pressure readings at pressure port (5) .

   Note: There may be air in the signal network, if there is a hesitation before reaching the relief pressure. Purge the signal lines of the air.

7. If the pressure is not within the specification, the signal relief valve will need adjusted. Refer to "Adjustment of the Signal Relief Valve For the Backhoe". If the pressure is within the specification, stop the engine and perform the "High Pressure Stall Test for the Loader".

Adjustment of the Signal Relief Valve For the Backhoe

If the system pressure is out of the specification during the stall test, then adjust the signal relief valve.

Illustration 6	g02177056
Bank valve for the backhoe (C) Signal relief valve for the backhoe

Illustration 7	g02177061
Inlet for the backhoe valve (C) Signal relief valve for the backhoe (13) Cap (14) Adjustment screw

1. Remove plastic cap (13) in order to access the M4 allen screw for adjusting.

2. Rotate M4 allen screw (14) in order to change the setting. Make small rotations at a given time.

   Note: Do not adjust more than a quarter turn.

   Note: Rotate adjustment screw (14) clockwise in order to increase the pressure setting. Rotate adjustment screw (14) counterclockwise in order to decrease the pressure setting.

3. Install plastic cap (13) .

High Pressure Stall Test for the Loader

1. Ensure that the work tool on the front of the machine and the stabilizers are on the ground. Engage the parking brake.

2. Start the engine. Run the engine at 1200 RPM.

3. Move the loader control to the RAISE position and the loader bucket to the RACK BACK in order to initiate the stall condition for the loader. Note the pressure reading at pressure tap (5). See Table 2 for the proper pressure readings at pressure port (5) .

4. If the pressure is not within the specification, the signal relief valve needs to be adjusted. Refer to "Adjustment of the Signal Relief Valve For the Loader".

5. Stop the engine and remove the gauges.

Adjustment of the Signal Relief Valve For the Loader

If the system pressure is out of the specification during the stall test, then adjust the signal relief valve for the loader.

Illustration 8	g02176648
Bank valve for the loader (D) Signal relief valve for the loader

The signal relief valve for the loader is located in the inlet cover of the loader valve on the bottom side. The signal relief valve for the loader is in the same location for single tilt and parallel lift valves. Also, the signal relief valve for the loader is in the same location for two and three bank valves.

Illustration 9	g02176844
Inlet of the loader valve (D) Signal relief valve for the loader (15) Cap (16) Allen head screw for adjusting

1. Remove cap (15) in order to access adjustment screw (16) .

2. Rotate allen head screw (16) in order to change the setting. Make small rotations at a given time.

   Note: Do not adjust more than a quarter turn.

   Note: Rotate adjustment screw (16) clockwise in order to increase the pressure setting. Rotate adjustment screw (16) counterclockwise in order to decrease the pressure setting.

3. Install plastic cap (15) after adjustment.

Adjustments for the Pump Controller

Illustration 10	g02177217
(17) Adjustment screw (18) Flow compensator spool (19) Nut (20) Nut (21) Pressure compensator spool (22) Adjustment screw

Flow Compensator Spool Adjustment

If the Margin Pressure is not within the specification, then do the following procedure.

1. Lower the work tool on the front of the machine. Engage the parking brake.

2. Stop the engine.

3. Move all the hydraulic hand controls through all of the positions in order to release pressure in the hydraulic system.

4. Connect one end of the 1U-5793 Pressure Differential Gauge to pressure tap (5) for the system pressure. Connect the other side of the pressure differential gauge to signal pressure tap (4) .

5. Repeat the "Margin Pressure Test". If the margin pressure is within specifications, then go to Step 10.

6. Loosen nut (19) .

7. Rotate adjustment screw (17) .

   Note: Rotate adjustment screw (17) clockwise in order to increase the margin pressure setting. Rotate adjustment screw (17) counterclockwise in order to decrease the margin pressure setting.

8. Tighten nut (19) .

9. Repeat the "Margin Pressure Test" until the margin pressure is within the specification.

10. Lower the implements to the ground. Stop the engine and engage the parking brake.

11. Remove all test equipment.