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Hot hydraulic oil under high pressure can remain in the components of the hydraulic system or the power train system after the engine has been stopped. The uncontrolled release of the hydraulic oil can cause sudden machine movement and can also result in the following conditions:
If hydraulic oil penetrates body tissue, the injury must be treated immediately by a doctor who is familiar with this type of injury. Use a board or a piece of cardboard to check for a hydraulic oil leak. Make sure that all of the attachments have been lowered to the ground and that all trapped pressure has been released from the hydraulic system and the power train system. Also, make sure that the hydraulic oil is cool before the removal of any components or lines. Remove the hydraulic oil filler cap only when the engine is stopped and the filler cap is cool enough to touch with your bare hand. |
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Personal injury can result if the machine moves while testing. If the machine begins to move during test, reduce the engine speed immediately and engage the parking brake. |
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| 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. |
Specifications
| Relief Valve (Charge) | ||
| Date | Equipment ID Code | |
| Item | Specification | Actual |
| Engine Speed before Stall | High idle | |
| Charge Pressure | 3300 ± 140 kPa (478 ± 20 psi) |
|
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| Illustration 1 | g01913055 |
| Torque Specifications | |
|---|---|
| Callout | Torque |
| Relief valve (1) | 70 N·m (52 lb ft) |
| Required Parts | ||
|---|---|---|
| Part Number | Description | Qty |
| 215-7697 | Shim Kit | 1 |
Introduction
The relief valve for the charge circuit maintains pressure in the charge circuit. The charge pump keeps the high-pressure steering loop full by supplying cooled, filtered oil. The steering loop is closed. The loop requires additional oil due to internal leakage. The pump also provides pressure and flow for the implement pilot circuit.
Required Tools
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| Illustration 2 | g02571852 |
Tooling (A) 198-4240 Digital Pressure Indicator Gp | |
| Required Tools | ||||
|---|---|---|---|---|
| Tool | Item | Qty | Part No | Description |
| A | 198-4240 | Digital Pressure Indicator Gp | ||
| A1 | 1 | 198-4234 | Digital Indicator | |
| A2 | 1 | 198-4238 (1) | Pressure Sensor Gp (0 to 34,450 kPa (0 to 5,000 psi)) |
|
| A3 | 1 | 198-4236 | Adapter Cable As | |
| ( 1 ) | This sensor must be purchased separately, the sensor is not included in the 198-4240 Digital Pressure Indicator Gp |
Test Preparation - Charge Pressure Relief Valve
- Move the machine to a smooth, horizontal location that is away from operating machines and away from personnel.
- Permit only one operator on the machine. Keep all other personnel away from the machine or in the sight of the operator.
- Place the steering control lever in the NEUTRAL position.
- Engage the parking brake.
- Lower the attachments to the ground.
- Stop the engine.
- Turn the key to the ON position, but do not start the engine.
- Verify that the implement shutoff control is in the UNLOCKED position.
- Move the implement control levers and the transmission control lever through the full range of travel several times. Movement of the implement control levers will relieve any pressure that may be present in the implement hydraulic system and the power train system.
- Loosen the filler cap on the hydraulic tank so that the pressure in the tank is released. The machine may be equipped with a breaker valve. The breaker valve will be located on top of the tank. To release the pressure in the tank, press the button on top of the breaker valve.
- Tighten the filler cap on the hydraulic tank.
- Make sure that the pressure in the entire hydraulic system has been released.
ReferenceFor additional guidance with preparing the machine for testing, refer to the Testing and Adjusting manual or the Troubleshooting manual for your machine.
Note: The monitoring system (if equipped) for your machine accesses many values that are useful in troubleshooting the hydraulic system. When the situation is appropriate, use the monitoring system in order to find a pressure or determine a system problem.
- Open the access door on the left side of the machine.
- Attach tooling (A) to pressure tap (P9) .
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| Illustration 3 | g01778877 |
(P9) "H" Pressure of steering charge pump at the filter outlet | |
Test Procedure - Charge Pressure Relief Valve
- Perform steps in the "Test Preparation - Charge Pressure Relief Valve" section.
- Start the engine. Warm the hydraulic oil to 45° ± 15°C (113° ± 27°F).
- Operate the engine at HIGH IDLE.
- Leave the controls in the NEUTRAL position. Record the pressures at pressure taps (P9) .
- Read the engine speed and the pressure at pressure taps (P9). Record the engine speed and the pressure at taps (P9) into Table 1 of the "Specifications". The pressure at tap (P9) should be 3300 ± 140 kPa (478 ± 20 psi).
- If the charge pressure is higher or lower than the specification, then the charge pressure relief valve could be faulty or out of adjustment.
- If the pressure at tap (P9) is out of the specification range and the steering controls are in the NEUTRAL position, the reason may appear below.
- There is a faulty charge relief valve in the steering pump.
- The cold start valve is faulty.
- The motor flushing valve is worn or stuck open.
- There is a worn motor.
- There is a worn steering pump.
- The charge pump has failed.
- There is a faulty charge relief valve in the steering pump.
Adjustment Procedure - Charge Pressure Relief Valve
- Stop the engine. Remove the floorplate.
- Locate the relief valve for the charge oil pressure (1) on the steering pump.
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| Illustration 4 | g01913053 |
- Remove charge oil relief valve (1) .
| | |
| Illustration 5 | g01913055 |
The pump is removed from the machine for clarity. | |
- Determine the number of shims (2) that are required to increase the charge oil pressure or determine the number of shims that are required to decrease the charge oil pressure.
- One 0.3 mm (0.012 inch) shim equals approximately 120 kPa (17 psi).
- One 0.5 mm (0.02 inch) shim equals approximately 200 kPa (29 psi).
- One 1 mm (0.04 inch) shim equals approximately 400 kPa (58 psi).
- One 0.3 mm (0.012 inch) shim equals approximately 120 kPa (17 psi).
Note: The charge oil relief valve is not a cartridge valve assembly. The charge oil relief valve is composed of individual parts. Ensure that none of the parts are lost when the relief valve is removed.
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| Illustration 6 | g01913079 |
- Remove shims and/or add shims.
- Install charge oil relief valve (1). Tighten the relief valve to 70 N·m (52 lb ft).
- Perform the test for the charge oil pressure. Refer to "Test Procedure - Charge Pressure Relief Valve".
- Repeat Step 1 through Step 7 of the "Adjustment Procedure - Charge Pressure Relief Valve" until the charge oil relief valve is set to the correct specification.