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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. |
| 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, PERJ1017, "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: Use the information in the reference to prepare the machine for this test. Also, use the information in the reference to relieve any hydraulic pressure that may be in the steering system.
Reference: For the correct procedure to relieve any hydraulic oil pressure that may be in the steering system, refer to the Service Manual module for Testing and Adjusting, "System Pressure - Release" for the machine that is being tested.
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When the compensator is rebuilt, make sure that the pressure compensator adjustment is backed out to a low pressure setting before the engine is started. Otherwise, severe pump and system damage can result. |
| Specifications | |
|---|---|
| Type | Range |
| Discharge Pressure | |
| Load Sense Pressure | |
| Margin Pressure | |
Pump discharge pressures are known values that can be found under specific conditions. The first condition is a test of margin pressure during operation of the bucket. The second condition is the high-pressure stall.
The high-pressure stall test indicates if the load sensing relief valve or the pressure compensator needs to be adjusted. The margin pressure test indicates if the flow compensator needs to be adjusted.
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| Illustration 1 | g01879273 |
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Tooling (D) | |
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| Illustration 2 | g06268366 |
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Tooling (F) | |
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| Illustration 3 | g06268689 |
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Tooling (G) | |
| Required Tools | ||||
|---|---|---|---|---|
| Tool | Item | Part Number | Part Description | Qty |
| D | 1U-5796 | Pressure Differential Tool Gp | ||
| D1 | 177-7861 | Hose As | 2 | |
| D2 | 6V-4143 | Quick Connect Coupler | 4 | |
| D3 | 6V-3965 | Fitting | 3 | |
| D4 | 6V-4144 | Quick Connect Coupler | 1 | |
| D5 | 8T-0861 | Pressure Gauge ( |
1 | |
| D6 | 8C-8431 | Tee | 1 | |
| D7 | 1U-5796 | Oil Filter Pressure Differential Gauge Gp | 1 | |
| D8 | 6V-0484 | O-Ring Adapter | 1 | |
| F | F1 | 187-3547 | Quick Disconnect Coupler As | 1 |
| F2 | 3J-1907 | O-Ring Seal | 1 | |
| F3 | 166-2033 | Tee As | 1 | |
| G | G1 | 2R-6806 | Adapter | 1 |
| G2 | 3J-1907 | O-Ring Seal | 2 | |
| G3 | 5I-3190 | Fitting | 1 | |
| G4 | 6V-3965 | Fitting (TEST) | 1 | |
Reference: Refer to Special Instruction, SEHS8979, "Component Identification and Calibration of the 1U5796 Differential Pressure Gauge Group" for more information on using Tooling (D).
- Install steering frame lock (1).
Refer to Operation and Maintenance Manual, "Steering Frame Lock" for more information on the machine that is being serviced.
- Engage the parking brake. Move the transmission direction selector to the NEUTRAL position.
- The engine should be at high idle throughout the warmup procedure. Continuously stall the TILT BACK position while simultaneously raising the lift arms at full speed. When the lift arms are almost raised, cycle the tilt cylinder to the FULL DUMP position. Then cycle to the TILT BACK position. Continuously stall the TILT BACK function and simultaneously lower the lift arms back to ground level. Without stalling the rack back function, cycle lift function to raise and lower the lift arms. This procedure will allow the pump to operate at low pressure and circulate oil throughout the system. Repeat this procedure until the hydraulic oil is at normal operating temperature.
Note: During the following step, do not keep the steering pump at stall condition for more than 10 seconds. If necessary, release the STIC steering control lever and wait for 30 seconds before you repeat the step.
- After the oil has reached normal operating temperature, position the bucket slightly off the ground. Run the engine at high idle.
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| Illustration 4 | g06138525 |
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Steering Frame Lock Installed | |
Testing Procedure-Steering Discharge Pressure
- Navigate the menu list to display the steering pump discharge pressure.
- Menu>Service>Parameters>Steering
- Move the STIC steering joystick control lever to the right to command full articulation. Continue to move the STIC steering joystick control lever in the full articulation position to obtain a reliable pressure reading.
Show/hide table
Illustration 5 g06247971 - Record the pressure reading on the monitoring system display. Refer to Table 1.
- Lower the work tool to the ground. Stop the engine.
- If the pressure reading is correct, no adjustment is required.
Adjustment Procedure Steering Discharge Pressure
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| Illustration 6 | g06295460 |
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Right Side View of Machine (2) Adjustment screw for steering cutoff pressure (3) Pressure and flow compensator valve | |
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| Illustration 7 | g06295462 |
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(2) Adjustment screw for steering cutoff pressure
(3) Pressure and flow compensator valve (4) Pressure cut off spool (5) Locknut | |
- Remove the cover from the adjustment screw (2). Loosen locknut (5). Turn the adjustment screw (2) clockwise to increase the pump discharge pressure. Turn the adjustment screw (2) counterclockwise to decrease the pump discharge pressure. One turn of the adjustment screw equals approximately
2800 kPa (406 psi) . - After you turn adjustment screw (2), hold adjustment screw in place, tighten locknut (5).
- Repeat Steps 1 through 2 until you obtain the correct pressure.
- Replace the cover on adjustment screw (2).
- Lower the work tool to the ground. Stop the engine.
- Relieve the hydraulic pressure.
Reference: For the correct procedure to relieve any hydraulic oil pressure that may be in the steering system, refer to the Service Manual module for Testing and Adjusting, "System Pressure - Release" for the machine that is being tested.
Test Preparation - Margin Pressure
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| Illustration 8 | g06271675 |
- With the machine off and the pressure bled out the hydraulics, install Tooling (F) to load sense line (1). Remove pressure switch (2) and install Tooling (G). Connect Tooling (D) to Tooling (F) and Tooling (G) Connect the high-pressure side to Tooling (G) and the low-pressure side to Tooling (F).
Show/hide table
Illustration 9 g06271679 Steering frame lock installed - Install steering frame lock (3).
Reference: Refer to Operation and Maintenance Manual, SEBU9952, "Steering Frame Lock" for more information on the machine being serviced.
- Engage the parking brake. Move the transmission direction control switch to the NEUTRAL position.
- The engine should be at high idle throughout the warmup procedure. Continuously stall the TILT BACK position while simultaneously raising the lift arms at full speed. When the lift arms are almost raised, cycle the tilt cylinder to the FULL DUMP position. Then cycle to the TILT BACK position. Continuously stall the TILT BACK function and simultaneously lower the lift arms back to ground level. Without stalling the rack back function, cycle lift function to raise and lower the lift arms. This procedure will allow the pump to operate at low pressure and circulate oil throughout the system. Repeat this procedure until the hydraulic oil is at operating temperature.
- After the oil has reached normal operating temperature, lower the work tool to the ground. Stop the engine.
Testing Procedure - Steering Pump Margin Pressure
- Move the steering frame lock to the STORED position.
- Start the engine. Raise the work tool until the work tool is slightly off the ground. Run the engine at low idle.
- Fully articulate the machine.
- Turn the steering control in the opposite direction of articulation to the PARTIALLY TURNED position (10% to 25% steering command). Record the margin pressure of Tooling (D5). Refer to Table .
Note: Margin pressure must be read during machine articulation. Once the machine stops articulating, you are not reading margin pressure. Margin pressure is the difference between the steering pump pressure and the signal pressure.
- The needle on Tooling (D5) will bounce between readings, but the needle should stabilize at
2100 ± 100 kPa (305 ± 15 psi) . Record the pressure reading on the pressure gauge. refer to Table . - Run the machine at low idle. Lower the work tool to the ground. Stop the engine.
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| Illustration 10 | g06271682 |
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Steering frame lock (3) in the STORED Position | |
Adjusting the Flow Compensator
- With the engine turned off, remove the cover from the adjustment screw (4). Loosen locknut (7). Turn adjustment screw (4) clockwise to increase the margin pressure. Turn adjustment screw (4) counterclockwise to decrease the margin pressure. One turn of adjustment screw (4) changes margin pressure by approximately
1415 kPa (205 psi) . - After you turn adjustment screw (4), hold adjustment screw in place and tighten locknut (7). Torque locknut (7) to a torque of
17 ± 3 N·m (150 ± 26 lb in) . - Repeat "Testing Procedure - Steering Pump Margin Pressure" until you obtain the correct margin pressure from the steering pump.
- Replace cover on the adjustment screw (4).
- Lower the work tool to the ground. Stop the engine.
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| Illustration 11 | g06138884 |
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Right side view of machine (4) Adjustment screw for steering margin pressure (5) Flow compensator valve (6) Steering pump | |
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| Illustration 12 | g06138886 |
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(4) Adjustment screw for steering margin pressure
(5) Pressure and flow compensator valve (7) Locknut (8) Margin spool | |