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 cylinders, and check valve for damage.
1. Make sure the steerlock anti-pivot link is released.
2. Check the level of oil in the hydraulic tank. Add oil if it is low. Check the lines, hoses, connections, and components for leaks.
3. Check oil delivery from steer pump.
4. Check HMU for damage or excessive wear.
5. Examine check valve (CP/CS-433B only) for correct operation.
6. Check steer cylinders for damage or excessive wear.
7. Steer pivot assembly or steer cylinders may be improperly lubricated. Bushings 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 check valve or steer cylinders.
1. Check the level of oil in the hydraulic oil tank. 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. Examine check valve (CP/CS-433B only) for correct operation.
8. Check steer cylinders for damage or excessive wear.
9. Check hydraulic lines and hoses for restrictions.
10. Steer pivot assembly or steer cylinders may be improperly lubricated. Bushings 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 cylinders for damage or excessive wear.
PROBLEM 4: Pump makes noise and steer cylinder rods do 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 tank. 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: 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. 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.
3. Check the type of oil used in the system. Refer to the Operation and Maintenance Guide.
4. Remove and inspect the pump. Check it for wear and be sure that it is assembled correctly. Check the relief valve inside pump for damage.
PROBLEM 7: 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 oil tank. 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.
4. Look for an obstruction in the oil cooler assembly.
PROBLEM 8: Excessive pressure at return filter.
PROBABLE CAUSE:
This problem could be caused by a restriction in the filter or in the return line to the hydraulic tank.
1. Replace filter element.
2. Check return filter for an obstruction or damaged parts.
3. Look for a restriction in the return line to the hydraulic oil tank.
Test Procedures
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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 hydraulic system. |
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1. Move the machine to a smooth horizontal location. Move away from working machines and personnel and lower implements to the ground.
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.
4. Stop the engine.
5. Move the hydraulic control levers to all positions to release the pressure in the hydraulic system.
6. Carefully loosen the filler cap on the hydraulic tank to release the pressure in the tank.
7. Make sure all hydraulic pressure is released before any fitting, hose or component is loosened, tightened, removed or adjusted.
8. Tighten the filler cap on the hydraulic tank.
9. The pressure in the system has now been released and lines or components can be removed.
During a diagnosis of the hydraulic system, remember that correct oil flow and pressure are necessary for correct operation. The output of the pump (oil flow) increases with an increase in engine speed (rpm) and decreases when engine speed (rpm) is decreased. Oil pressure is caused by resistance to the flow of oil.
When troubleshooting a possible problem in the steer 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.
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Some of the following tests and adjustments are performed with the machine engine operating. When these tests are done away from the operator's station, two people must be working. One person performs the tests and adjustments, and the other should be at the controls. This will help prevent accidental movement of machine. |
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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 hole leaks. |
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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 inspection of the hydraulic system and its components is the first step when a diagnosis of a problem is made. Stop the engine, lower the blade to the ground. To remove the tank filler cap, slowly turn the filler cap until it is loose. If oil comes out the bleed hole, let the tank pressure lower before the filler cap is removed. Make the following inspections:
1. Measure the oil level.
2. Look for air in the oil that is in the 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 filter elements and look for particles removed from the oil by the filter element. A magnet will separate ferrous particles from nonferrous particles (piston rings, o-ring seals, etc.).
4. Inspect all oil lines and connections for damage or leaks.
5. Inspect control linkage for bent, broken or damaged components.
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 inlet line of a flow meter to hose (2) of HMU. Install outlet line of flow meter to hose (1).
3. Open the manual load valve (on flow meter) fully.
4. Start engine and run at full throttle.
5. Slowly close manual load valve (on flow meter) to set system pressure at 6900 kPa (1000 psi).
6. Observe flow meter. Record pump output reading.
7. Shut engine OFF. Ensure all hydraulic pressure is removed from the system. Disconnect flow meter.
8. Reconnect hydraulic hose (2) to pressure port (3). Reconnect hydraulic hose (1) to tank port (4).
9. Pump output recorded in step 6 should be approximately 30 liters/min (8 U.S. gpm). If pump output is less than 23 liters/min (6 U.S. gpm) there is a problem. Check the following:
a. On CP/CS-433B, examine the check valve for correct operation.
b. On CP/CS-433B, check the secondary/parking brake for leakage.
c. Perform System Pressure Test located in this module.
d. Check steer pump for damage or excessive wear.
10. If pump output recorded in step 6 is more than 30 liters/min (8 U.S. gpm), the priority valve in the steer pump may not be working. Check steer pump for damage or excessive wear.
System Pressure Test
Hand Metering Unit (HMU)
(1) Hydraulic hose. (2) Pressure port.
1. Place the steerlock anti-pivot link in the locked position to prevent machine from turning.
2. Disconnect hydraulic hose (1) from pressure port (2) of HMU.
3. Install a tee into pressure port (2). Connect hydraulic hose (1) to tee. Install a 0 to 28 000 kPa (0 to 4000 psi) pressure gauge with a hose and fitting, to tee.
4. Start engine and run at approximately 1/4throttle.
5. Turn the steering wheel. Hold the wheel in a turn position until relief valve (in steer pump) opens.
6. Observe pressure gauge. Note the indication on the gauge. Correct pressure reading is 13 800 kPa (2000 psi).
7. If pressure reading is over 13 800 kPa (2000 psi) the relief valve (located in steer pump) should be adjusted or replaced.
8. If pressure reading is less than 13 800 kPa (2000 psi) check the following:
a. Relief valve (in steer pump) may need to be adjusted or replaced.
b. Steer pump may be damaged or not getting enough oil.
c. HMU may be damaged.
d. Steer cylinder(s) may have excessive internal leakage.
e. On CP/CS-433B check secondary/parking brake for leakage.
9. Shut engine OFF. Make sure all hydraulic pressure is removed from the system.
10. Disconnect tee and pressure gauge. Connect hydraulic hose (1) to pressure port (2).
11. Unlock the steerlock anti-pivot link and place it in the storage position.
Steering Time Check
1. Park the machine on a dry, hard surface.
2. Place the steerlock anti-pivot link in the unlocked position, allowing the machine to turn.
3. Start engine and run at full throttle.
4. Count the number of steering wheel revolutions and the time required for a full right turn from stop to stop.
5. Count the number of steering wheel revolutions and the time required for a full left turn from stop to stop.
6. The time required for a full turn in step 4 and step 5 should be equal. A full turn should require no more than 5.5 seconds, corresponding to 5 revolutions of the steering wheel.
7. If steering time or number of revolutions exceeds maximum, the HMU may need to be repaired or the steer cylinder(s) may have excessive internal leakage.
Cylinder Leakage Test
Hand Metering Unit (HMU)
(1) Hydraulic hose. (2) Left turn port.
1. Start engine and run at full throttle.
2. Place the steerlock anti-pivot link in the unlocked position, allowing the machine to turn.
3. Turn the steering wheel for a right turn until the steer cylinders are against their stops.
4. Shut engine OFF. Make sure all hydraulic pressure is removed from the system.
5. Disconnect hydraulic hose (1) from left turn port (2) of HMU. Place end of hose in a pail to catch any oil leakage.
6. Install a plug, capable of withstanding 2070 kPa (300 psi), into left turn port (2) of HMU.
7. Start engine and run 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 .5 liters/min (.13 U.S. gpm), one or both steer cylinders is leaking across the piston, and should be repaired or replaced.
10. Shut engine OFF.
11. Reconnect hydraulic hose (1) to left turn port (2) of HMU.