Troubleshooting
PROBLEM 1: Pump makes noise and blade 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 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 2: 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 short rapid duty cycle, 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. If the duty cycle of the blade is short and fast, the temperature of the oil can become high. Maximum hydraulic oil temperature is 93° C (200° F).
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 3: 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, Form No. KEBU2846.
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.
5. Check engine rpm at full throttle. If the engine is not operating at rated rpm, pump output will be reduced.
PROBLEM 4: Oil pressure in the system is too low.
PROBABLE CAUSE:
This problem is normally caused by leakage in the system, the opening pressure of a relief valve that is too low, or a damaged pump.
1. Carefully check the system for leakage. Remember that leakage inside a hydraulic component may be hard to see.
2. Check the operation of the relief valve in the blade control valve.
3. Check blade cylinder for leakage or excessive wear.
4. Remove and inspect the steer pump for damage and correct assembly.
PROBLEM 5: Oil pressure in the system is too high.
PROBABLE CAUSE:
Excessive oil pressure in the system can be caused by excessive mechanical friction in one of the components. Otherwise, the relief valve may be misadjusted, or the control valve may be damaged.
1. Check the operation of the relief valve in the blade control valve.
2. Inspect the blade control valve for damage or internal contamination.
3. Blade cylinder pivot points and blade pivot pins may be improperly lubricated. Pivot bushings may be damaged. Refer to the Operation and Maintenance Guide for lubrication information.
4. Check blade cylinder for damage or excessive wear.
PROBLEM 6: Loss of efficiency in the system (slow cylinder movement and loss of pressure).
PROBABLE CAUSE:
The probable cause for this problem is normally the same as the causes for Problems 3 and 4. Low oil output from the pump, leakage in the system, and the opening pressure of the relief valve is too low. Check Problems 3 and 4 for solutions to this problem. Also check control lever for full travel of control valve spool.
PROBLEM 7: Blade position drifts when control lever is in HOLD position.
PROBABLE CAUSE:
This problem could be caused by damage or excessive wear in the blade control valve or the blade cylinder.
1. Inspect the blade control valve for damage or internal contamination.
2. Check operation of control lever. Make sure spring in control valve will move control lever to the HOLD position.
3. Check blade cylinder for leakage or excessive wear.
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 leveling blade system, perform the Visual Checks first. Then do the Operation Checks. If these checks indicate a problem, or if there is a different problem in the system, 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.
Operation Checks
The operation checks can be used to find leakage in the system. They can also be used to find a bad valve or pump. The speed of cylinder rod movement can be used to check the condition of the cylinder and the pump.
1. Start the engine, following proper operating procedures. Run the engine at full throttle.
2. Raise and lower the blade several times.
a. Watch the cylinder as the rod extends and retracts. Movement must be smooth and regular.
b. Check for unusual or excessive noise from the pump.
c. Check for the sound of the relief valve opening. The opening pressure of the relief valve is given in System Pressure Test, located in this module.
3. Lower the blade to the ground.
4. Measure the time required for the blade to raise completely, when the control lever is held in the UP position.
5. With the blade fully raised, measure the time required to lower the blade completely, when the control lever is held in the DOWN position.
6. Time required to raise the blade should be approximately 6 seconds. Time required to lower the blade should be approximately 4 seconds.
7. If travel time is too slow, or if blade does not operate properly, refer to Troubleshooting and the following Tests and Adjustments to identify and solve the problem.
Pump Efficiency Test
Blade Control Valve
(1) Return hose. (2) Outlet port. (3) Inlet port. (4) Pressure hose.
1. Disconnect pressure hose (4) from inlet port (3) of blade control valve. Disconnect return hose (1) from outlet port (2) of blade control valve. Mark the two hoses for reassembly. Plug the two ports on the blade control valve to prevent contaminants from entering.
2. Install inlet line of a flow meter to pressure hose (4). Install outlet line of flow meter to return hose (1).
3. Open the manual load valve (on flow meter) fully.
4. Start engine and run at full throttle.
5. Slowly close the manual load valve (on flow meter) to set system pressure at 5516 kPa (800 psi).
6. Observe flow meter. Record pump output reading.
7. Shut engine OFF. Make sure all hydraulic pressure is removed from the system. Disconnect flow meter.
8. Reinstall pressure hose (4) to inlet port (3). Reinstall return hose (1) to outlet port (2).
9. Pump output in step 6 should be approximately 61 liters/min (16 U.S. gpm). If pump output is less than 53 liters/min (14 U.S. gpm), refer to Troubleshooting for probable cause and remedy.
System Pressure Test
Blade Control Valve
(1) Inlet port. (2) Pressure hose.
1. Disconnect pressure hose (2) from inlet port (1) of blade control valve.
2. Install a tee into inlet port (1). Connect pressure hose (2) to tee. Install a 0 to 21 000 kPa (0 to 3000 psi) pressure gauge with a hose and fitting, to tee.
3. Start engine and run at full throttle.
4. Keep blade control lever in the HOLD position. Observe pressure gauge. Record pressure reading on the following table.
5. Pull blade control lever back to the UP position. Observe the pressure gauge as the blade is raising. Record pressure gauge reading on the table.
6. Keep blade control lever in the UP position after the blade is completely raised. Observe pressure gauge. This is the relief valve setting. Record pressure reading on the table.
7. Push blade control lever forward to the DOWN position. Observe the pressure gauge as the blade lowers. Record pressure reading on the table.
8. Push blade control lever past the DOWN position to the detent. This is the FLOAT position. Observe the pressure gauge. Record the pressure reading on the table.
9. Shut engine OFF. Make sure all hydraulic pressure is removed from the system.
10. Disconnect tee and pressure gauge. Connect pressure hose (1) to inlet port (2) of blade control valve.
- a. Oil pressure in the HOLD position should be approximately 2070 kPa (300 psi).
- b. Oil pressure in the UP position should be approximately 4830 kPa (700 psi).
- c. Relief valve pressure setting should be approximately 8620 kPa (1250 psi).
- d. Oil pressure in the DOWN position should be approximately 2760 kPa (400 psi).
- e. Oil pressure in the FLOAT position should be approximately 2070 kPa (300 psi).
- b. Oil pressure in the UP position should be approximately 4830 kPa (700 psi).
11. Compare the recorded pressures on the above table, with the following:
12. If the relief valve setting is too high or too low, the relief valve should be adjusted. See Relief Valve Adjustment, located in this module.
13. If the oil pressure in HOLD or FLOAT is too high, check the blade control valve for damage.
14. If the oil pressure in UP or DOWN is too high, check the blade control valve for damage, check the blade cylinder for damage, check the cylinder pivot points, and the blade pivot pins for damaged bushings or improper lubrication.
Relief Valve Adjustment
Blade Control Valve
(1) Cap. (2) Adjusting screw. (3) Jam nut.
1. Perform System Pressure Test, located in this module. Leave the pressure gauge installed to the blade control valve.
2. Remove cap (1) from the blade control valve. Loosen jam nut (3).
3. Turn adjusting screw (2) in (clockwise) to increase pressure setting, or out (counterclockwise) to decrease pressure setting.
4. Repeat System Pressure Test and step 3, if necessary, until relief valve setting is correct. If the above procedure does not change the relief valve setting, the relief valve components may need to be replaced.
5. Tighten jam nut (3) while holding adjusting screw (2) to prevent it from turning.
6. Replace cap (1).
Cylinder Leakage Test
Blade Cylinder
(1) Hydraulic hose. (2) Retract port.
1. Start engine.
2. Push blade control lever forward to lower the blade completely.
3. Shut engine OFF.
4. Make sure all hydraulic pressure is released from the system. Disconnect hydraulic hose (1) from retract port (2) of the blade cylinder.
5. Install a plug, capable of withstanding 4140 kPa (600 psi), into end of hose (1).
6. Start engine and run at full throttle.
7. Push blade control lever forward to the DOWN position. No more than a trickle of oil should leak from retract port (2).
8. If leakage is in excess of .5 liters/min (.13 U.S. gpm) internal cylinder leakage is too much. The blade cylinder should be repaired or replaced.
9. Shut engine OFF. Remove plug from end of hose (1).
10. Connect hydraulic hose (1) to retract port (2) of the blade cylinder.