259D Skid Steer Loaders Machine Systems – Visual Inspection

------ WARNING! ------

Escaping fluid under pressure, even a pinhole size leak, can penetrate body tissue, causing 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.



Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting and repair of the machine. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids.

Refer to Special Publication, NENG2500, "Caterpillar Tools and Shop Products Guide", for tools and supplies suitable to collect and contain fluids in Caterpillar machines.

Dispose of all fluids according to local regulations and mandates.


A visual inspection of the system is the first step when beginning the troubleshooting process.

Test Preparation

Before any tests are performed, prepare the machine. Refer to Testing and Adjusting, "Machine Preparation". Before any tests are performed, visually inspect the complete hydraulic system for oil leaks and damaged parts. Refer to Testing and Adjusting, "Visual Inspection".

Note: The oil in the hydraulic system must be at an operating temperature of 50° ± 10°C (122° ± 18°F). This temperature range is specified for standard factory fill oil only. Use the Electronic Technician Software in order to monitor this temperature. Or refer to Testing and Adjusting, "Hydraulic Oil Temperature Test" for an alternate procedure.

Test Procedure

  1. Check the hydraulic oil level in the sight glass for the hydraulic tank.

  1. Look for water in the oil.

  1. Add oil to the hydraulic system, if necessary. Refer to the Operation and Maintenance Manual for the recommended oil and for the correct procedure.

  1. Check all lines, all hoses, and all connections for damage and for leaks. Look for fluid on the ground under the machine.

    Note: If fluid can leak out of a fitting or out of a connection, air can leak into the system.

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