Troubleshooting

Troubleshooting can be difficult. A list of possible problems and probable causes is on the pages that follow.

This list of problems and probable causes will only give an indication of where a problem can be and what repairs are needed. Normally, more or other repair work is needed beyond the recommendations on the list. Remember that a problem is not necessarily caused only by one part, but by the relation of one part with other parts. This list cannot give all possible problems and probable causes. The serviceman must find the problem and its source, then make the necessary repairs.

The 4C4892 ORFS Fittings Group can be used to make pressure tests of the steering system. Before any tests are made, visually inspect the complete hydraulic system for leakage of oil and for parts that are damaged. For some of the tests a magnet and a mm (in) measuring rule will be needed.

When any test is made of the steering hydraulic system, the hydraulic oil must be at the normal temperature for operation.

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Sudden movement of the machine or pressure oil release can cause injury to persons on or near the machine. To prevent possible injury, do the procedure that follows before testing and adjusting the steering hydraulic system.

1. Move the machine to a smooth horizontal location. Move away from working machines and personnel. Stop the engine.

2. Permit only one operator on the machine. Keep all other personnel either away from the machine or in view of the operator.

3. Activate the parking brake.

NOTE: During certain performance tests it will be necessary to release the parking brake to help drum movement when turns are required.

4. Make sure all hydraulic pressure is released before any fitting, hose or component is loosened, tightened, removed or adjusted.

Visual Checks

A visual inspection of the steering system and its components is the first step when a diagnosis of a problem is made. Stop the engine, make the following inspections.

1. Measure the oil level.

2. Look for air in the oil that is in the hydraulic tank. Do this immediately after the machine is stopped. Use a clear bottle or container to get a sample of the oil. Look for air bubbles in the oil that is in the bottle.

3. Remove the hydraulic filter element and look for particles removed from the oil by the filter element.

4. Check all oil lines and connections for damage.

Operation Checks

Operation checks of the steering system can be used for a diagnosis of poor performance and to find the source of oil leakage inside the hydraulic system.

Problem: Steering pump makes noise and the steering cylinder rods do not move smoothly.

Probable Cause:

1. Air in the steering hydraulic circuit.

2. The steering pump is worn.

3. Loose oil line connection on the inlet side of the steering pump.

4. Low oil level in the hydraulic oil tank.

5. Viscosity of the hydraulic oil is wrong.

Problem: Too much force is needed to turn the steering wheel.

Probable Cause:

1. Relief valve is open.

2. Low oil level in the hydraulic oil tank.

3. Steering pump oil pressure is too low, caused by a worn steering pump.

4. Steering control unit covers are too tight.

5. Steering control unit is defective.

6. Hydraulic oil is cold.

7. Alignment of steering column is not correct.

Problem: Machine does not turn when steering wheel is turned.

Probable Cause:

1. Low oil level in the hydraulic oil tank.

2. Air in the hydraulic system.

3. Dirt in the hydraulic system.

4. Steering pump operation is not correct.

5. Frame articulation is locked because the lock pin is in position.

Problem: Machine turns too slow in both directions.

Probable Cause:

1. Not enough oil flow from steering pump.

2. Steering pump suction line is restricted.

3. Steering control unit operation is not correct.

4. Seal leakage in the steering cylinders.

5. Priority valve spool inside steering pump does not allow enough oil to go to the steering control unit.

Problem: Machine turns too slow in one direction.

Probable Cause:

1. Restriction in steering control unit.

Problem: The steering control unit does not return to center position correctly.

Probable Cause:

1. Steering control unit covers are too tight.

2. Alignment of the steering column is not correct.

3. Valve spool in the steering control unit has a restriction.

Problem: Temperature of hydraulic oil is too hot.

Probable Cause:

1. Viscosity of the hydraulic oil is wrong.

2. Air is mixed with the hydraulic oil.

3. Steering system relief valve has a defect.

4. There is a restriction in the one of the steering system lines or components.

Problem: Steering wheel turns without the operator turning it.

Probable Cause:

1. Foreign material causes the sleeve valves in steering control unit to stick.

2. Centering springs are broken or damaged in the steering control unit.

3. Timing of the steering control unit drive is not correct. The drive must be timed as follows.

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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 as follows.

Steering Control Unit Drive Timing
(1) Cross pin. (2) Rotor tooth used for alignment. (3) Rotor. (4) Stator.

Cross pin (1) must align with the bottom of rotor tooth (2).

Pump Efficiency Check

For any pump test at a given rpm, the pump flow at 690 kPa (100 psi) will be larger than the pump flow at 6900 kPa (1000 psi). The difference between the pump flow of the two operating pressures is the flow loss.

Flow loss when expressed as a percent of pump flow is used as a measure of pump performance.

If the percent of flow loss is more than 10%, pump performance is not good enough.

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^*Numbers in examples are for illustration and are not values for any specific pump or pump condition. See Specifications for pump flow of a new pump at 690 kPa (100 psi) and 6900 kPa (1000 psi).

Machine Test

Install a Flow Meter. For Formula I, measure pump flow at 690 kPa (100 psi) and at 6900 kPa (1000 psi) with the engine at high idle rpm.

Bench Test

If the test bench can be run at 6900 kPa (1000 psi) and at full pump rpm, find the percent of flow loss using Formula I.

If the test bench cannot be run at 6900 kPa (1000 psi) and at full pump rpm, run the pump shaft at 1000 rpm. Measure the pump flow at 690 kPa (100 psi) and at 6900 kPa (1000 psi). Use these values in the top part of Formula II. For the bottom part of the formula, run the pump shaft at 2000 rpm. Measure the pump flow at 690 kPa (100 psi).

Steering System Pressure Check

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Make reference to WARNING on first page of Troubleshooting.

Frame Lock Pin Installed
(1) Lock pin. (2) Yoke.

1. Apply the parking brake.

2. Install frame lock pin (1) in the hole provided in articulation yoke (2).

3. Remove the two side panels from the right side of the operator's compartment.

Steering Pump
(3) Load sensing pressure line.

Steering Pump
(4) Bottom pressure line.

4. Disconnect load sensing pressure line (3) or bottom pressure line (4) on the steering pump. Install a tee and the 0 to 25 000 kPa (0 to 3600 psi) pressure gauge from the fittings group. Connect the load sensing pressure line to the tee. This pressure gauge will measure the steering relief valve pressure setting.

5. Start and run the engine at 2200 rpm.

6. Turn the steering wheel to the left until the steering relief valve opens. Record the reading on the gauge. The relief valve pressure should be 18 950 ± 690 kPa (2750 ± 100 psi).

Steering Pivot Clearance Adjustments

Earlier

Later Steering Pivot
(1) Pivot pin. (2) Bearing plate.

Procedure to shim upper pivot pin (1):

Steering pivot clearance check .8 mm (.03 in) while prying the pivot assembly up.

Procedure to shim bearing plate (2):

Shim bearing plate for .05 mm (.002 in) to .25 mm (.010 in) clearance at bearing shoulder with opposite bearing against shoulder.

Clearance Checks

NOTE: After installation of the drum assembly, the clearance between the vertical bushings and vertical pins must be checked. Use the following procedure:

Vertical Steer Pivot Clearance

Check the vertical steer pivot clearance as follows:

1. Put the machine on a hard level surface. Stop the engine, and apply the secondary brake.

2. Attach the base of 8T5098 Dial Indicator to the top of the steer pivot housing as shown. Set the dial indicator actuator on the top of the rear frame.

3. Set the dial indicator to zero.

4. Place a hydraulic jack under the rear frame at the pivot assembly.

5. Raise the hydraulic jack and record the reading on the dial indicator.

NOTE: When adding or removing spacers only the top pivot point is shimmed.

6. With new bearings and shims installed, total movement should be .13 to 1.14 mm (.005 to .045 in) on a used machine, total vertical movement should not exceed 1.91 mm (.075 in). If the movement is too much, the clearance can be reduced by adding spacers at the vertical pin joints. If the movement is too small, the clearance can be increased by removing spacers at the vertical pin joint.

7. If the proper clearance cannot be obtained with the spacers, the steer pivot housing should be disassembled. Bushings or any other worn components should be replaced.

Horizontal Steer Pivot Clearance

Check the horizontal steer pivot clearance as follows:

1. Put the machine on a hard level surface. Stop the engine, and apply the secondary brake.

2. Attach the base of 8T5098 Dial Indicator or equivalent to the top of the steer pivot housing. Set the dial indicator actuator against the front face of the rear frame.

3. Set the dial indicator to zero.

4. Place a hydraulic jack under the rear frame at the pivot assembly.

5. Raise the hydraulic jack and record the reading on the dial indicator.

6. With the new bearings, bushings and pins the total movement recorded should be .10 to .76 mm (.004 to .030 in). On a used machine the total movement should not exceed 1.27 mm (.050 in).

7. If the movement is too much, the steer pivot housing should be disassembled. Bushings, bearings and any other worn components should be replaced.

Oscillation Bearing Clearance

Check the oscillation bearing clearance as follows:

NOTE: During assembly, it is recommended that this clearance measurement be made prior to installing the drum into the yoke.

1. Put the machine on a hard level surface. Stop the engine, and apply the secondary brake.

2. Attach the base of 8T5098 Dial Indicator to the front face of the steer pivot bearing plate (2). Set the dial indicator actuator against the front face of the oscillation shaft.

3. Insert a long, heavy pry bar between the yoke assembly and the steer pivot housing. Push hard on the pry bar to move the drum and yoke assembly as far forward as possible.

4. With the dial indicator actuator set against the front face of the plate, set the dial indicator to zero.

5. Insert a long, heavy pry bar between the yoke assembly and the plate. Push hard on the pry bar to move the drum and yoke assembly back toward the rear frame. Observe the dial indicator and record the reading.

NOTE: When removing or adding shims behind the plate, remove or add equal amounts at the top and bottom of the plate.

6. Total movement should be .05 to .25 mm (.002 to .010 in) on a new assembly. The maximum reading for a used assembly should be .51 mm (.020 in). If the movement is too much, the clearance can be reduced by removing shims from behind the plate. If the clearance is too small, shims can be added to increase the clearance.

NOTE: Inadequate bearing lubrication may result if zero endplay or a preload condition is present.

7. If the proper clearance cannot be obtained with the removal or addition of shims, the oscillation assembly should be disassembled. Bushings and any other worn components should be replaced.