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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. |
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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. |
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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: Prior to examining the hydraulic system review the hydraulic schematic and the System Operation/Test and Adjust manual for the 844K:
- Hydraulic Schematic, UENR4895, "844K Wheel Dozer (T4F & LRC) Hydraulic System Schematic"
- System Operation/Test & Adjust, UENR4599, "844K (T4F & LRC) Wheel Dozer Machine Systems Operation/Testing & Adjusting "
The 8T-5320 Hydraulic Test Group or the 1U-5481 Pressure Gauge Group can be used to test the hydraulic system pressure. Before any tests are performed, visually inspect the entire hydraulic system for oil leaks and for damaged parts. For some of the tests, a magnet and a measuring rule (millimeters or inches) are usable tools.
Before tests are performed, visually inspect the entire implement system for oil leaks and for damaged components. Also, inspect the entire hydraulic fan system for oil leaks or damaged components.
When you diagnose a problem in the implement system, a visual inspection of the hydraulic system is the first step.
Note: When any test is performed on the steering system, the hydraulic oil must be at normal operating temperature. To increase the oil temperature, start the engine and turn the machine in both directions. Also, raise the implement and lower the implement.
Stop the engine and lower the implement to the ground. Release the pressure in the implement system and in the hydraulic fan system.
Perform the following inspections:
- Check the oil level in the hydraulic tank.
- Check for air in the hydraulic oil immediately after the engine is stopped. Look for air bubbles in the oil that is in the container.
Locate the Fluid Sampling Valve near the pilot pump for the machine.
- Purge the fluid sampling valve. Insert an 8T-9208 Probe Assembly into the fluid sampling valve. Draw a 50 mL oil sample through the fluid sampling valve into a suitable container. The level of contaminants must be lower than the values in the following table.
Note: Use approximately
150 mm (6 inch) length of tube on the end of the probe.Reference: Refer to Special Publication, PEHP6001, "How To Take A Good Oil Sample" for more information about obtaining an oil sample.
- Check for flow restrictions in all oil lines. Flow restrictions include bends in the oil lines, clamps that are not installed correctly, and damage to hoses and to lines. Check all hydraulic connections for damage and for leaks.
- Inspect all of the control linkages for damage.
- Remove the filter elements and check the elements for particles. Use a magnet to separate ferrous particles from nonferrous particles.