Sudden movement of the machine or release of oil under pressure can cause injury to persons on or near the machine. To prevent possible injury, perform the procedure that follows before testing and adjusting the hydraulic system. |
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. |
NOTICE |
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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. |
Note: Put identification marks on all lines, on all hoses, on all wires, and on all tubes for installation purposes. Plug all lines, all hoses, and all tubes to prevent fluid loss and to keep contaminants from entering the system.
There is a main relief valve in bank valve group. The pressure spool of the compensator valve acts as a main relief for backhoe operation. The pressure spool of the compensator valve limits the system pressure to
Do not increase the pressure compensator valve in an attempt to set the line relief valves that are set above the pump compensator spool setting. The line relief valves are sensitive to flow and the line relief valves cannot be accurately set with the hydraulic pump.
The line relief valves must be removed from the machine. The line relief valves may need to be bench tested if the line relief valves are set above the main relief setting.
Prior to removing the line relief valve, perform the swing test, the test for the implement, and the test for the stabilizer cycle time. Then, perform the margin pressure test, the low-pressure standby test, and the high-pressure stall test. If a function is still suspected, stall that function and listen for the line relief valve to open. If the line relief valve does not open, then the line relief valve is set above the system pressure. Check the line relief valve pressure settings in order to verify that the line relief valves are within the specifications.
Illustration 1 | g03616838 |
This is the location of the backhoe control valve.
Remove the floor plates in order to gain access to the top of the backhoe control valve. Refer to Disassembly and Assembly, "Floor plates - Remove and Install".
Illustration 2 | g03591260 |
This is the location of the loader control valve.
Remove the floor plates in order to gain access to the top of the loader control valve. Refer to Disassembly and Assembly, "Floor plates - Remove and Install".
Mechanically Operated Controls
Two Bank Valve for the Loader Control
Illustration 3 | g03589580 |
(1) Base end line relief valve for the tilt control valve
(2) Rod end line relief valve for the tilt control valve (3) Steering priority valve |
Six Bank Valve for the Backhoe Control
Illustration 4 | g03589581 |
(1) Head end line relief valve for the stick control
(2) Head end line relief valve for the bucket control (3) Right swing circuit line relief valve for the swing control (4) Rod end line relief valve for the boom control (5) Rod end line relief valve for the stick control (6) Rod end line relief valve for the bucket control (7) Left swing circuit line relief valve for the swing control (8) Head end line relief valve for the boom control |
Required Tools | ||
Part Number | Description | Quantity |
8T-0860 | Pressure Gauge |
1 |
3S-6224 | Electric Hydraulic Pump Gp | 1 |
8F-0024 | Hose As | 2 |
1P-2375 | Quick Connect Coupler | 2 |
1P-2376 | Quick Connect Coupler | 2 |
1P-2377 | Plug As | 2 |
7J-8611 | Pipe Elbow | 1 |
3B-7722 | Pipe Bushing | 2 |
030-8370 | Pipe Adapter | 2 |
1U-5216 | Test Manifold Block | 1 |
- Use the following steps in order to test or check the appropriate relief valve setting.
- Lower all of the work tools and the stabilizers to the ground.
- Stop the engine.
- Turn the key to the ON position and move all of the control levers to all of the positions to release the system pressure.
- Turn the key to the OFF position.
- Remove the line relief valve that will be tested.
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Illustration 5 g03130837 (1) Test manifold block
(2) Line relief valve
(3) Pipe adapter
(4) Quick connect coupler
(5) Quick connect coupler
(6) Hose assembly - Secure 1U-5216 Test Manifold Block (1) in a suitable holding device.
- Install two 030-8370 Pipe Adapter (3) and two 1P-2375 Quick Connect Coupler (4) in 1U-5216 Test Manifold Block (1).
- Attach two 1P-2376 Quick Connect Coupler (5) to two 8F-0024 Hose As (6).
- Install line relief valve (2) in 1U-5216 Test Manifold Block (1).
- Connect two 8F-0024 Hose As (6), two 3B-7722 Pipe Bushing, and 7J-8611 Pipe Elbow to 3S-6224 Electric Hydraulic Pump Gp.
- Connect 8T-0860 Pressure Gauge to 3S-6224 Electric Hydraulic Pump Gp.
- Turn the 3S-6224 Electric Hydraulic Pump Gp to the ON position. Check for leaks at the connection.
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NOTICE The 3S-6224 Electric Hydraulic Pump only has a
7.6 L (2 US gal) reservoir. Pump damage may result if the pump is operated with an empty reservoir. - Slowly increase the pressure. Record the pressure, when the line relief valve opens. Compare this pressure to Table 2 or 3.
- Stop the pump.
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Table 2 Line Relief Valve Pressure Settings Cylinder Circuit Setting Auxiliary for the Loader Head end for the Auxiliary Cylinder Loader Tilt Circuit for the Single Tilt Machine Rod end for the Dump Operation 30000 kPa (4351 psi) Head end for the Tilt Back Operation Show/hide tableTable 3 Line Relief Valve Pressure Settings Cylinder Circuit Setting Backhoe Boom Head end to LOWER 19200 kPa (2785 psi) Rod end to RAISE 27000 kPa (3916 psi) Backhoe Swing Rod end to Swing LEFT 30000 kPa (4351 psi) Rod end to Swing RIGHT Backhoe Bucket Head end of the Bucket Cylinder 27000 kPa (3916 psi) Rod end of the Bucket Cylinder Backhoe Stick Head end for retracing the Stick IN 30000 kPa (4351 psi) Rod end for extending Stick OUT - If the line relief valve is within the specification, then go to Step 18. If the line relief valve is not within the specification, then an adjustment is required.
- Remove cap (7). Loosen locknut (9) and turn adjusting screw (8) clockwise in order to increase pressure. Turn adjusting screw (8) counterclockwise in order to decrease pressure.
- Check the oil level in 3S-6224 Electric Hydraulic Pump Gp and refill the oil if it is necessary. Repeat Steps 13, 14, 15, and 16.
Show/hide tableIllustration 6 g03132517 Relief valve
(7) Cap
(8) Adjusting screw
(9) Locknut - Tighten locknut (9) to a torque of
20 ± 3 N·m (177 ± 27 lb in) . - Remove line relief valve (2).
- Install a new O-ring on line relief valve (2).
- Install the line relief valve in control valve to a torque of
45 ± 5 N·m (33 ± 4 lb ft) .
- Engage the boom lock.
- Run the engine at the low idle. See Table 4 for the appropriate engine speed.
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Table 4 Machine Sales Model Engine rpm 424B 1200 rpm - Push the boom control lever fully forward in order to activate the BOOM LOWER circuit.
- Note the pressure reading at pressure tap.
- Refer to Table 5 for the proper pressure readings at pressure port.
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Table 5 Hydraulic Circuit Pressure BOOM LOWER 18800 to 19600 kPa (2727 to 2843 psi) - Lower the work tools to the ground. Engage the parking brake and stop the engine.
Note: By using the gauge, small leakage problems such as a cut seal or a missing seal can be detected.