422E, 428E, 432E, 434E, 442E and 444E Backhoe Loaders Hydraulic and Steering System Caterpillar

Show/hide table

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.

Show/hide table

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	g01274096
(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	g01274126
(5) System pressure tap

The system pressure tap (5) is located at the bottom of the pump. 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" in this 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.
   Show/hide table
   
   

   Illustration 3	g00869466

   1. Remove two bolts (6) and plate (7) .
   Show/hide table
   
   

   Illustration 4	g00869467

   2. Remove two bolts (8) and plate (9). Remove floor mat (10) .
   Show/hide table
   
   

   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 the pressure tap (5) for system pressure. Install one hose assembly to the 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 the signal pressure tap (4) should be approximately 500 kPa to 1500 kPa (70 psi to 220 psi). This pressure is the steering signal pressure. The steering signal pressure is not adjustable. If the steering signal pressure is in the range, proceed to Step 10.

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

9. If the steering signal pressure is out of the range, remove the test equipment and cycle the steering. Then, perform the test again. If the steering 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 the pressure tap (5) is the low standby pressure. The low standby pressure should be approximately 2000 kPa to 3600 kPa (290 psi to 520 psi).

    Note: If the standby 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.

Margin Pressure Test

1. Install a 8T-0860 Pressure Gauge with a range of 0 to 40000 kPa (0 to 5800 psi) to each hose assembly. Install one hose assembly to the pressure tap (5) for system pressure. Install one hose assembly to the signal pressure tap (4) .

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. Subtract the pressure at signal pressure tap (4) from the pressure at system pressure tap (5). This is the margin pressure. The margin pressure should be 2150 kPa to 2450 kPa (312 psi to 355 psi). If the margin pressure is out of the specification, then refer to "Flow Compensator Spool Adjustment" in "Adjustments for the Pump Controller".

6. Stop the engine.

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

Note: Do not remove test equipment. The test equipment is required for the "High Pressure Stall Test".

High Pressure Stall Test

High Pressure Stall Test for the Backhoe

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

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

3. Start the engine. Run the engine at 1200 rpm.

4. Move the boom control to the boom up in order to initiate a stall condition for the boom. Note the pressure reading at pressure tap (5) .

5. 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.

6. 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 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	g01276059
Bank Valve for the backhoe (C) Signal relief valve for the backhoe

Illustration 7	g01282284

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

2. Rotate the 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 the screw for adjusting (14) clockwise in order to increase the pressure setting. Rotate the screw for adjusting (14) counterclockwise in order to decrease the pressure setting.

3. Install the 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 tilt control for the loader in order to tilt the bucket. Stall the bucket in a rack position. 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	g01275889
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	g01276020
(D) Signal relief valve for the loader (15) plastic cap (16) Allen Head Screw for adjusting

1. Remove the plastic cap (15) in order to access the screw for adjusting (16) .

2. Rotate the 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 the screw for adjusting (16) clockwise in order to increase the pressure setting. Rotate the screw for adjusting (16) counterclockwise in order to decrease the pressure setting.

3. Install the plastic cap (15) after adjustment.

Adjustments for the Pump Controller

Illustration 10	g01274171
Compensator valve (17) Flow compensator spool (18) Set screw (19) O-ring (20) Set screw (21) Adjustment screw (22) Adjustment screw (23) O-ring (24) Pressure compensator spool

Illustration 11	g01274686

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. Install two 8T-0860 Pressure Gauges with a range of 0 to 40000 kPa (0 to 58000 psi) to the pressure tap (5) for the system pressure and 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 set screw (20) .

7. Rotate adjustment screw (21) .

   Note: Rotate the screw for adjusting (21) clockwise in order to increase the margin pressure setting. Rotate the screw for adjusting (21) counterclockwise in order to decrease the margin pressure setting.

8. Tighten set screw (20) .

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.