Usage:
Troubleshooting
PROBLEM 1: Machine does not turn when steering wheel is turned.
PROBABLE CAUSE:
This problem may be caused by a lack of output oil from the pump. Otherwise, check the HMU, steer cylinder, and front bolster group for damage.
1. Check the level of oil in the hydraulic tank. Add oil if it is low. Check the lines, hoses, connections, and components for leaks.
2. Nut holding steering wheel may be loose or stripped. Steering wheel may be damaged.
3. Steer pump drive belt may be loose or broken.
4. Pump drive pulley connections could be broken.
5. Check oil delivery from steer pump.
6. Check HMU for damage or excessive wear.
7. Check steer cylinder for damage or excessive wear.
8. Front bolster group or steer cylinder may be improperly lubricated. Bushings or bearings may be worn out or damaged.
PROBLEM 2: Steering wheel is hard to turn.
PROBABLE CAUSE:
This could be caused by poor output from the pump, incorrect assembly or damage to the HMU, or damage to the front bolster group or steer cylinder.
1. Check the level of oil in the hydraulic reservoir. Add oil if it is low. Check the system for leaks.
2. Hydraulic oil may be too cold.
3. Check oil delivery from steer pump.
4. Bolts may be too tight on metering section of HMU.
5. Check timing of HMU metering section. Pin (1) must align with high point (3) of external pump gear (2).
HMU Metering Section
(1) Pin. (2) External pump gear. (3) High point.
6. Check HMU for damage or excessive wear.
7. Check steer cylinder for damage or excessive wear.
8. Check hydraulic lines and hoses for restrictions.
9. Front bolster group or steer cylinder may be improperly lubricated. Bushings or bearings may be worn out or damaged.
PROBLEM 3: Machine turns too slowly.
PROBABLE CAUSE:
Slow steering could be caused by poor output from the pump, damage to the HMU, contamination, or leakage in the system.
1. Check oil delivery from steer pump.
2. Check hydraulic lines and hoses for restrictions.
3. Check HMU for contaminants or internal damage.
4. Check steer cylinder for damage or excessive wear.
PROBLEM 4: Pump makes noise and steer cylinder rod does not move smoothly.
PROBABLE CAUSE:
The probable cause of excessive noise from the pump is air in the system. The noise is caused by aeration (air bubbles at the inlet side). Excessive noise may also be caused by a low setting on a relief valve.
1. Check the level of oil in the hydraulic reservoir. If the level of the oil is below the return line, air can leak in when the pump is working.
2. Check the hose and connections between the tank and the pump for leaks. If oil can leak out when the machine is sitting idle, air can leak in when the pump is working.
3. Another cause of air in the oil is low oil viscosity. Refer to the Operation and Maintenance Guide to make sure the correct oil is used.
4. In cold weather, the oil may be too thick to flow to the pump. Run engine until hydraulic system is warmed up and noise disappears.
5. Check steer pump for damage or incorrect assembly.
PROBLEM 5: Machine turns by itself, or steering wheel rotates without operator turning it.
PROBABLE CAUSE:
The most likely cause of this problem is a problem in the HMU. Look for internal contamination, broken parts, or incorrect assembly.
1. Mounting bolts for HMU may be too tight.
2. Bolts may be too tight on metering section of HMU.
3. Contamination inside HMU could cause components to stick.
4. Check HMU for internal damage or excessive wear.
PROBLEM 6: Machine will not stay in a straight line.
PROBABLE CAUSE:
This could be caused by air in the hydraulic system, or by damage to the steer cylinder or the HMU.
1. Check a sample of the oil for air bubbles. Find and correct the source of air leakage.
2. Examine the steer cylinder for a bent rod or damaged internal parts.
3. Check HMU for damage or excessive wear.
PROBLEM 7: Oil delivery by the pump is not according to specifications.
PROBABLE CAUSE:
Reduced pump output may be caused by a restriction in the supply line to the pump, or a low oil level in the tank. If the viscosity of the oil is too high, there will be a decrease in the flow of oil from the pump. A badly worn pump or one that has not been correctly assembled will also cause reduced output flow.
1. Check the level of oil in the hydraulic oil tank. Add oil if it is low.
2. Steer pump drive belt may be loose or broken.
3. Pump drive pulley connections should be broken.
4. Check the supply line to the pump for a restriction. Check the tank to be sure there is not a restriction in the supply line to the pump.
5. Check the type of oil used in the system. Refer to the Operation and Maintenance Guide.
6. Remove and inspect the pump. Check it for wear and be sure that it is assembled correctly. Check the relief valve and control section inside pump for damage.
PROBLEM 8: The oil in the system gets too hot.
PROBABLE CAUSE:
The common causes of heat in a hydraulic system are: low oil level in the tank, a pressure setting on a relief valve that is too low, a restriction in a line that causes an orifice effect, or excessive mechanical friction.
1. Check the level of oil in the hydraulic reservoir. Add oil if it is low. Check the lines, hoses, connections, and components for leaks.
2. Check the operation of the relief valve in the steer pump. If it is stuck open or malfunctioning, high oil temperature will result.
3. Check the system for a restriction in an oil line. A restriction in the pump supply line will reduce the flow of oil to the pump and cause the pump to become very hot. A restriction in a line that is between the pump and the implements will cause a reduction in efficiency and high oil temperature. Removal of the restriction will normally solve the problem.
Test Procedures
 |
Sudden movement of the machine or release of oil under pressure 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 system. |
 |
1. Move the machine to a smooth horizontal location. Move away from working machines and personnel.
2. Permit only one operator on the machine. Keep all other personnel either away from the machine or in view of the operator.
3. Engage the parking brake.
4. Stop the engine.
5. Move the steering wheel to all positions to release the pressure in the hydraulic lines and components.
6. Make sure all hydraulic pressure is released before any fitting, hose, or component is loosened, tightened, removed, or adjusted.
When troubleshooting a possible problem in the steering system, perform the Visual Checks first. If a problem is still indicated, perform the other tests and adjustments as necessary to identify and solve the problem.
|
To prevent possible personal injury, when tests are made with the machine moving, make sure only one operator is on the machine. Keep other personnel away from the machine. Make sure tests are done in a flat and open area. |
|
NOTE: Some of the following tests and adjustments require measurements of hydraulic oil flow or pressure. The machine should be operated until the engine and hydraulic oil are at normal operating temperature before these measurements are taken.
|
Do not check for leaks with your hands. Pin hole (very small) leaks can result in a high velocity oil stream that will be invisible close to the hose. This oil can penetrate the skin and cause personal injury. Use cardboard or paper to locate pin holes. |
|
Reference: Be sure to follow correct safety practices when performing procedures covered in this module. See Safety Page, Form No. SENR7733.
Visual Checks
A visual check of the steering system and its components is the first step when a diagnosis of a problem is made. Park the machine on level ground and stop the engine. Make the following inspections:
1. Remove the cap on the hydraulic reservoir and check the oil level. Hydraulic oil should be at the FULL mark inside the reservoir and the oil should be clean.
2. If the oil appears clean but the level is low, add fresh oil as instructed in the Operation and Maintenance Guide for the machine.
3. If the oil is dirty or contaminated, the oil must be replaced.
- * Check the color of the amber in color. When dirty, the color darkens to blackish brown.
- * Considerable darkness, burnt odor, or an opaque quality of the oil indicates chemical breakdown. Replace the oil.
- * A milky appearance indicates water in the oil. Correct the source of water leakage and replace the oil.
- * After the sample stands overnight, sediment at the bottom of the oil indicates a collapsed, ruptured or clogged filter.
- * Considerable darkness, burnt odor, or an opaque quality of the oil indicates chemical breakdown. Replace the oil.
4. If there is any uncertainty regarding oil condition, obtain a sample of the oil from the hydraulic tank. Check the oil for the following qualities:
5. Check for signs of oil leakage on steering system components, and on the ground under the machine.
6. Check inside the hydraulic reservoir. Look for particles at the bottom of the reservoir. Metal particles may indicate a failure in the pump or HMU. Rubber particles indicate a seal failure.
7. If metal or rubber particles are found, all components of the steering system must be cleaned and the lines flushed. Replace the oil.
Pump Efficiency Test
Hand Metering Unit (HMU)
(1) Hydraulic hose. (2) Hydraulic hose. (3) Pressure port. (4) Tank port.
1. Disconnect hydraulic hose (2) from pressure port (3) of HMU. Disconnect hydraulic hose (1) from tank port (4) of HMU. Mark the two hoses for reassembly. Install caps into ports (3) and (4) to prevent contaminants from entering.
2. Install the inlet line of a flow meter to hose (2). Install the outlet line of the flow meter to hose (1).
3. Open the manual load valve (on flow meter) fully.
4. Start the engine and allow time for the system to warm up. Make sure the parking brake is engaged.
5. Make sure the transmission shift lever is in the Neutral position.
6. Move the shuttle lever to the right. Push the lever forward to run the engine at full throttle.
7. Slowly close the manual load valve (on flow meter) to set system pressure at 3450 kPa (500 psi).
8. Observe the flow meter. Record pump output reading.
9. Move the shuttle lever back to the Neutral position.
10. Shut the engine off. Make sure all hydraulic pressure is removed from the system.
11. Disconnect the flow meter from hydraulic hoses (1) and (2).
12. Reconnect hydraulic hose (2) to pressure port (3). Reconnect hydraulic hose (1) to tank port (4).
13. Pump output recorded in step 8 should be approximately 19 liters/min (5 U.S. gpm). If pump output is less, there is a problem. Check the following:
a. Control section of steer pump may be damaged.
b. Perform System Pressure Test located in this module.
c. Check steer pump for damage or excessive wear.
14. If pump output recorded in step 8 is more than 15 liters/min (4 U.S. gpm), the control section in the steer pump may not be working. Check the steer pump for damage or excessive wear.
System Pressure Test
Hand Metering Unit (HMU)
(1) Hydraulic hose. (2) Pressure port.
1. Park the machine with the front wheels in a full right turn position.
2. Shut the engine off. Make sure all hydraulic pressure is removed from the system.
3. Disconnect hydraulic hose (1) from pressure port (2) of HMU.
4. Install a tee into pressure port (2). Connect hydraulic hose (1) to the tee. Install a 0 to 13 800 kPa (0 to 2000 psi) pressure gauge with a hose and fitting, to the tee.
5. Start the engine and allow time for the system to warm up. Make sure the parking brake is engaged.
6. Make sure the transmission shift lever is in the Neutral position.
7. Move the shuttle lever to the right. Push the lever forward to run the engine at full throttle.
8. Observe the pressure gauge without turning the steering wheel. Record the pressure gauge reading on the following table.
9. Turn the steering wheel to the right turn position. Hold the wheel in position until relief valve (in steer pump) opens.
10. Observe the pressure gauge. This is the setting of the relief valve. Release the steering wheel and write the relief pressure in the following table.
11. Shut the engine off. Make sure all hydraulic pressure is removed from the system.
12. Disconnect the tee and pressure gauge. Reconnect hydraulic hose (1) to pressure port (2).
13. When the steering wheel is not being turned, system pressure should be less than 1380 kPa (200 psi). If the recorded pressure is too high, internal damage to the HMU could be restricting oil flow.
14. Relief valve setting should be 6900 kPa (1000 psi). If relief pressure is too high, the relief valve (located in steer pump) should be adjusted or replaced.
15. If relief pressure is too low, check the following:
a. Relief valve (in steer pump) may need to be replaced.
b. Steer pump may be damaged or not getting enough oil.
c. The HMU may be damaged.
d. Steer cylinder may have excessive internal leakage.
Steering Time Check
1. Park the machine on a dry, hard surface.
2. Start the engine and allow time for the system to warm up.
3. Make sure the parking brake is engaged.
4. Make sure the transmission shift lever is in the Neutral position.
5. Continue to run the engine at idle speed.
6. Count the number of steering wheel revolutions and the time required for a full right turn from stop to stop.
7. Count the number of steering wheel revolutions and the time required for a full left turn from stop to stop.
8. The turns in steps 6 and 7 should take approximately 9 seconds, corresponding to 8 revolutions of the steering wheel.
9. If steering time or number of revolutions is too high, but the Pump Efficiency Test checks out all right, check the following:
a. The HMU may be damaged or have excessive wear.
b. The steer cylinder may have excessive internal leakage.
c. Bearings in the front bolster group could be damaged or improperly lubricated
Cylinder Leakage Test
Hand Metering Unit (HMU)
(1) Hydraulic hose. (2) Left turn port.
1. Park the machine with the front wheels in a full right turn position.
2. Shut the engine off. Make sure all hydraulic pressure is removed from the system.
3. Disconnect hydraulic hose (1) from left turn port (2) of HMU. Place end of hose in a pail to catch any oil leakage.
4. Install a plug, capable of withstanding 13 800 kPa (2000 psi) into left turn port (2) of HMU.
5. Start the engine and allow time for the system to warm up. Make sure the parking brake is engaged.
6. Make sure the transmission shift lever is in the Neutral position.
7. Move the shuttle lever to the right. Push the lever forward to run the engine at full throttle.
8. Turn the steering wheel to the right. No more than a trickle of oil should leak from hose (1).
9. If leakage is in excess of .2 liters/min (.05 U.S. gpm), the steer cylinder has excessive internal leakage. Repair or replace the cylinder.
10. Shut the engine off.
11. Reconnect hydraulic hose (1) to left turn port (2) of HMU.