 |
Personal injury or death can result from sudden machine movement. Sudden movement of the machine can cause injury to persons on or near the machine. To prevent injury or death, make sure that the area around the machine is clear of personnel and obstructions before operating the machine. |
 |
|
Personal injury can result from hydraulic oil pressure and hot oil. Hydraulic oil pressure can remain in the hydraulic system after the engine has been stopped. Serious injury can be caused if this pressure is not released before any service is done on the hydraulic system. Make sure all of the attachments have been lowered, oil is cool before removing any components or lines. Remove the oil filler cap only when the engine is stopped, and the filler cap is cool enough to touch with your bare hand. |
|
| NOTICE |
|---|
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, "Caterpillar Tools and Shop Products Guide" for tools and supplies suitable to collect and contain fluids on Caterpillar products. Dispose of all fluids according to local regulations and mandates. |
Operational Checks
Note: The checks during operation can be used to find leakage in the system. These checks can also be used to find a bad valve, a bad pump, or a bad motor.
Probable Causes of Problems in the Steering System
Problem
The gear pump is noisy and the steering cylinder rods do not move easily.
Probable Cause
- Air in the steering hydraulic circuit
- The gear pump is worn.
- There is a loose connection in the oil line that is connected to the inlet side of the steering pump.
- The hydraulic oil level is low.
- Viscosity of the hydraulic oil is not correct.
Problem
Too much force is needed to turn the steering wheel.
Probable Cause
- The relief valve is open.
- The hydraulic oil level is low.
- The oil pressure in the gear pump is too low.
- Metering pump covers are too tight.
- The metering pump is defective.
- The hydraulic oil is cold.
- Alignment of steering column is not correct.
Problem
The machine does not turn when the steering wheel is turned.
Probable Cause
- The hydraulic oil level is low.
- There is air in the hydraulic system.
- There is dirt in the hydraulic system.
- The operation of the gear pump is not correct.
- The frame articulation is locked because the lock pin is in the hole in the yoke.
- One of the steering cylinders has worn piston rings.
Problem
The machine turns slowly in both directions.
Probable Cause
- There is not enough oil flow from the gear pump.
- The suction line in the gear pump is restricted.
- Metering pump operation is not correct.
- Seal leakage in the steering cylinders.
- The priority valve spool that is inside the gear pump does not allow enough oil to go to the metering pump.
- The pressure in the steering circuit is too low.
Problem
Machine turns slowly in one direction.
Probable Cause
- There is a restriction in the metering pump.
Problem
The metering pump does not return to the center position correctly. Probable Cause
- Metering pump covers are too tight.
- Alignment of the steering column is not correct.
- The valve spool in the metering pump has a restriction.
- One of the steering cylinders is not functioning properly.
Problem
Temperature of hydraulic oil is too hot.
Probable Cause
- Viscosity of the hydraulic oil is not correct.
- Air is mixed with the hydraulic oil.
- The relief valve in the steering system has a defect.
- There is a restriction in the one of the steering system lines or components.
- The oil cooler is plugged.
Problem
When the steering system pressure is tested, the system does not reach the relief valve pressure setting of 19000 ± 300 kPa (2750 ± 45 psi).
Probable Cause
- The relief valve is not properly shimmed.
- The relief valve is open.
- The relief valve is defective.
Problem
The steering wheel turns without manually turning the wheel.
Probable Cause
- Foreign material causes the spool valve in the metering pump to jam.
- Centering springs are broken or damaged in the metering pump.
- Timing of the metering pump drive is not correct.
- The temperature of the oil is too hot.
The following procedure will aid in the proper timing adjustment of the metering pump.
|
If the steering control unit drive is not timed correctly, the machine can turn in the opposite direction as the steering wheel. To prevent personal injury, loss of life and/or property damage, make sure the drive is timed correctly. |
|
 | |
| Illustration 1 | g00470238 |
Drive Timing of the Metering Pump. (1) Cross pin. (2) Rotor tooth. (3) Rotor. (4) Stator. | |
Cross pin (1) must align with the bottom of the rotor tooth (2) .