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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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Sudden movement or accidental starting of the machine can cause personal injury or death to persons on or near the machine. To prevent personal injury or death, perform the following: Park the machine on a smooth, level surface. Lower the work tool to the ground and engage the parking brake. Stop the engine and remove the key. Block the wheels and install the steering frame lock. |
| 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. |
| Pilot Pressure - Low Idle | |
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The pilot pressure for the fan / pilot system and on the 844K is provided by the fan /pilot pump. The pilot pressure is controlled by a pressure reducing valve.
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| Illustration 1 | g02571852 |
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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 | 198-4239 | Pressure Sensor Gp
(0 to 41,368 kPa (0 to 6,000 psi)) |
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| A3 | 1 | 198-4236 | Adapter Cable As | |
- Move the machine to a smooth, horizontal location that is away from operating machines and away from personnel.
- Place the transmission direction in the NEUTRAL position.
- Engage the parking brake.
- Lower the work tool to the ground.
- Stop the engine.
- Relieve the pressure in the hydraulic system.
Reference: For more information about relieving the hydraulic pressure, refer to the Service Manual module Testing and Adjusting, "System Pressure - Release" for the machine that is being serviced.
- Install the steering frame lock.
- Install tooling (A) to test port (1).
- Start the machine.
- Increase the engine speed to low idle.
- Observe the pilot pressure on tooling (A), the pressure should be
3705 ± 605 kPa (540 ± 90 psi) . - Lower the engine speed to low idle.
- Stop the engine.
- Remove tooling (A).
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| Illustration 2 | g03676509 |
Check complete.