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Sudden movement of the machine or release of oil under pressure can cause serious injury to persons on or near the machine. To prevent possible injury, perform the procedure that follows before testing and adjusting the hydraulic system. |
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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 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. |
The operational checks can be used to find a leak in the hydraulic system. The checks can also be used to detect a defective valve or a defective pump.
Warm the oil to a minimum temperature of 60 °C (140 °F). At least two segments should be visible on the bargraph for hydraulic oil temperature.
Extend the hydraulic cylinders and retract the hydraulic cylinders several times.
- Watch the hydraulic cylinders as the cylinders move. The movement of the cylinders should be smooth and regular.
- Listen for noise from the pump.
- A low pressure setting of the hitch relief valve can cause the hitch to lower during roading. A high pressure setting of the hitch relief valve can cause a reduction in the life of components of the hydraulic system.
- Allow the implement cylinders to travel the full stroke in each direction. Check the kickout of the detent.
- Place each control valve in the HOLD position while the implement or the hitch is off the ground. Watch for excessive cylinder rod drift.
Drift of the hydraulic cylinders can be caused by the following conditions: leakage of oil past the piston seals and too much clearance between the valve stem and the valve body.
Three-Point Hitch Cylinder Drift
Use the following procedure to check the three-point hitch cylinder drift. 0 to 4 mm (0 to 0.16 inch)
- Load the three-point hitch with 2270 kg (5000 lb).
- Fully raise the hitch.
- The following table shows the acceptable drift for the three-point hitch.
Show/hide table
Table 1 Three-Point Hitch Cylinder Drift Temperature Drift in 5 Minutes
49°C (120°F)
0 to 4 mm (0 to 0.16 inch)