980K Wheel Loader Electrohydraulic System Caterpillar

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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.

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Personal injury or death can result from escaping fluid under pressure. Escaping fluid under pressure, even a very small pin-hole size leak, can penetrate body tissue and cause serious injury and possible death. If fluid is injected into your skin, it must be treated immediately by a doctor familiar with this type of injury. Always use a board or cardboard when checking for a leak.

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Sudden movement or accidental starting of the machine can cause personal injury or death to persons on or near the machine. To prevent personal injury or death, perform the following: Park the machine on a smooth, level surface. Lower the work tool to the ground and engage the parking brake. Stop the engine and remove the key. Block the wheels and install the steering frame lock.

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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, "Dealer Service Tool Catalog" for tools and supplies suitable to collect and contain fluids on Cat products. Dispose of all fluids according to local regulations and mandates.

Note: This machine is equipped with an electronic control module (ECM). The ECM has the system diagnostics for detecting faults in the electronic control system. The diagnostics are displayed on the Caterpillar Monitoring System when the system is in the Service Mode. The diagnostics can also be displayed through Caterpillar Electronic Technician.

Make sure that all faults are cleared through the Caterpillar Monitoring System or Caterpillar Electronic Technician before you troubleshoot the following problems:

Problem 1: The pump makes noise and the cylinder rods do not move evenly. There are also air bubbles in the oil.

Probable causes:

1. The viscosity of the oil is incorrect.

2. The relief valve opens at low oil pressure.

3. There is a loose connection of the oil line on the inlet side of the pump.

4. The pump has too much wear.

Problem 2: The oil temperature is too high.

Probable causes:

1. The machine is being operated above the intended capacity or in ambient temperatures that are too high for the design of the machine.

2. The viscosity of the oil is incorrect.

3. The pump has too much wear.

4. There is a restriction in an oil passage.

5. There is a leak in one or more circuits.

6. The load on the system is too high. High load causes the relief valve to open.

7. The oil level is low.

8. The oil is contaminated.

9. The air flow through the oil cooler is too low.

10. The oil flow through the oil cooler is too low.

11. There is air in the hydraulic oil.

    Note: A problem with air in the hydraulic oil must be corrected before the hydraulic system will operate at normal temperatures. There are two conditions that cause air to be in the hydraulic oil:

    • Return oil is flowing into the hydraulic oil tank above the level of oil that is in the tank.

    • There are leaks in the line between the hydraulic pump and the hydraulic oil tank.

12. The recirculation seals are damaged. Damaged seals allow hot air to recirculate back through the oil cooler.

13. The hydraulic oil temperature sensor is not functioning properly.

14. Incorrect fan speed

Problem 3: The pump output flow is low.

Probable causes:

1. The oil level is low.

2. The viscosity of the oil is incorrect.

3. The pump has too much wear.

Problem 4: The oil pressure is low.

Probable causes:

1. The load sensing signal relief valve is not properly adjusted.

2. The high-pressure cutoff setting for the implement pump is not properly adjusted.

3. The load sensing signal is not arriving at the implement pump.

4. The pump has too much wear.

5. An O-ring seal in the system failed.

6. The control valve and the valve spool have excessive wear.

Problem 5: The work tool moves while the control lever is in the HOLD position.

Probable causes:

1. The control valve and the valve spool have excessive wear.

2. A piston seal in a cylinder has excessive wear.

3. There is a leak in a connection between the control valve and the cylinder that is drifting.

4. A check valve is not closing because of dirt or because of a worn seat.

5. The control valve is not centering correctly.

6. There may be dirt or the return spring may be broken.

7. The lever position sensor is not functioning properly.

8. One of the lever position sensors has moved since the last calibration.

9. One of the lever position sensors needs recalibration.

10. The solenoid valve for the pilot hydraulics needs replacement.

11. One of the lever position sensors needs replacement.

Problem 6: The lift cylinder droops when the lift control lever is moved from the HOLD position to the RAISE position.

Droop is an initial movement of the hydraulic cylinders. The movement is in the opposite direction that is commanded by the operator. The cylinders then move in the correct direction.

Probable causes:

1. The oil is too cold.

2. The piston seals and/or the lift cylinders are worn.

3. There is dirt or debris in the load check valve.

Problem 7: The hydraulic force is too low when the lift control lever is moved to the RAISE position or to the LOWER position.

Probable causes:

1. The machine is being operated improperly.

2. The pilot system pressure is too low.

3. The modulation current to the solenoid is not correct.

4. The lift position sensor is damaged or the sensor not calibrated properly.

5. The relief valve setting for the ride control valve is too low while the ride control switch is ON.

6. The main control valve is contaminated or damaged.

7. The makeup valve is sticking.

8. The load sensing signal relief valve setting is too low.

9. The load sensing resolver network is malfunctioning.

Problem 8: All implement functions are sluggish.

Probable causes:

1. The oil level is low.

2. The pump is worn or damaged.

3. The implement electronic control module is not calibrated.

4. The load sensing signal relief valve setting is too low.

5. The pressure reducing valve for pilot pressure is not functioning properly.

6. The hydraulic system is contaminated.

7. The pump control valve is malfunctioning.

8. The hydraulic lockout solenoid valve is malfunctioning.

Problem 9: The implement functions are erratic or intermittent.

Probable causes:

1. The oil level is low.

2. There is air in the hydraulic oil.

   Note: A problem with air in the hydraulic oil must be corrected before the hydraulic system will operate at normal temperatures. There are two conditions that cause air to be in the hydraulic oil:

   • Return oil is flowing into the hydraulic tank above the level of oil that is in the tank.

   • There are leaks in the oil suction line between the pump and the tank.

3. The pump has too much wear.

4. The implement electronic control module is not calibrated.

5. The pressure reducing valve for pilot pressure is not functioning properly.

6. The main control valve is contaminated or damaged.

7. There is dirt or debris in the load check valve.

Problem 10: There is too much lift cylinder drift.

Drift is a cylinder movement with the control lever or the joystick in the HOLD position.

Probable causes:

1. The modulation current to the solenoid is incorrect.

2. The ride control valve is worn or damaged.

3. The piston seals and/or the lift cylinders are worn.

4. An anti-drift valve in the main control valve is worn or damaged.

5. There is dirt or debris in the load check valve.

6. The lift lever sensor is not properly mounted. The lift lever sensor not calibrated properly.

7. The manual lowering valve is not closed completely.

Problem 11: The hydraulic force is too low when the tilt control lever is moved to the TILT BACK position or to the DUMP position.

Probable causes:

1. The machine is being operated improperly.

2. The position sensor for the tilt control lever is sending an incorrect signal.

3. The modulation current to the solenoid is incorrect.

4. The pressure reducing valve for pilot pressure is not functioning properly.

5. The settings of the line relief valves are too low.

6. The piston seals and/or the tilt cylinder is worn.

7. The main control valve is contaminated or damaged.

8. The load sensing signal relief setting is too low.

9. The pump control valve is malfunctioning.

Problem 12: The lift cylinders collapse during the raise operation.

Cylinder collapse is the sudden drop during normal operation.

Probable causes:

1. The lift control lever and/or the position sensor may be worn or damaged.

2. The modulation current to the solenoid is incorrect.

3. The pressure reducing valve for pilot pressure is not functioning properly.

4. The ride control valve may be worn or damaged.

5. The nitrogen precharge pressure in the ride control accumulator is too low.

6. The piston seals and/or the lift cylinders are worn.

7. The main control valve is contaminated or damaged.

8. The makeup valve is sticking.

9. There is dirt or debris in the load check valve.

Problem 13: There is low power to the implements.

Probable causes:

1. The machine is operating above the intended capacity.

2. The engine power is too low.

3. The pump has too much wear.

4. The modulation current to the solenoid is incorrect.

5. The implement electronic control system is not calibrated correctly.

6. The pressure reducing valve for pilot pressure has a low setting.

7. The load sensing signal relief valve setting is too low.

8. The settings of the line relief valves are too low.

9. The piston seals and/or the cylinders are worn.

10. The load check valve is damaged or contaminated.

11. A solenoid on the control valve group is not functioning properly.

Problem 14: There is too much tilt cylinder drift.

Drift is a cylinder movement with the control lever or joystick control in the HOLD position.

Probable causes:

1. The modulation current to the solenoid is incorrect.

2. The setting of the line relief valve is too low.

3. The piston seals and/or the tilt cylinder is worn.

4. An anti-drift valve in the main control valve is worn or damaged.

5. The load check valve is contaminated or damaged.

6. The tilt lever sensor is not properly mounted. The tilt lever sensor is not calibrated properly.

Problem 15: The tilt cylinders collapse during the tilt function.

Cylinder collapse is the sudden drop during normal operation.

Probable causes:

1. The modulation current to the solenoid is incorrect.

2. The pressure setting of the line relief valve for the tilt cylinder is too low.

3. The piston seals and/or the tilt cylinder is worn.

4. There is dirt or debris in the main control valve.

5. The main control valve spool and/or the mating surfaces may be worn or damaged.

6. The makeup valve is sticking.

Problem 16: The tilt cylinder droops during the tilt function.

Droop is an initial movement of the hydraulic cylinders. The movement is in the opposite direction that is commanded by the operator. The cylinders then move in the correct direction.

Probable causes:

1. The oil is too cold.

2. The piston seals and/or the tilt cylinder is worn.

3. There is dirt or debris in the load check valve.

Problem 17: There is too much drift in the auxiliary cylinders.

Drift is a cylinder movement with the control lever or the joystick control in the HOLD position.

Probable causes:

1. The modulation current to the solenoid is incorrect.

2. The setting of the line relief valve is too low.

3. The piston seals and/or the auxiliary cylinders are worn.

4. There is dirt or debris in the load check valve.

5. The main control valve is contaminated or damaged.

6. The auxiliary lever sensor is not properly mounted. The auxiliary lever sensor is not calibrated properly.

Problem 18: The auxiliary cylinders collapse during the auxiliary function.

Cylinder collapse is the sudden drop during normal operation.

Probable causes:

1. The modulation current to the solenoid is incorrect.

2. The setting of the line relief valve is too low.

3. The piston seals and/or the auxiliary cylinders are worn.

4. There is dirt or debris in the main control valve.

5. The main control valve spool and/or mating surfaces may be worn or damaged.

Problem 19: The auxiliary cylinder droops during the auxiliary function.

Droop is an initial movement of the hydraulic cylinders. The movement is in the opposite direction that is commanded by the operator. The cylinders then move in the correct direction.

Probable causes:

1. The oil is too cold.

2. The piston seals and/or the auxiliary cylinders are worn.

3. There is dirt or debris in the load check valve.

Problem 20: The hydraulic force is too low during auxiliary functions.

Probable causes:

1. The machine is being operated above the intended capacity.

2. The position sensor for the auxiliary control lever needs recalibration.

3. The implement electronic control module is not calibrated correctly.

4. The pressure reducing valve for pilot pressure is not functioning properly.

5. The setting of the line relief valve is too low.

6. The piston seals and/or the auxiliary cylinders are worn.

7. The main control valve spool and/or the mating surfaces are worn or damaged.

8. A solenoid valve for the pilot hydraulics is not functioning properly.

Problem 21: One implement function is sluggish or nonfunctional.

Probable causes:

1. The position sensors for the control levers are sending an incorrect signal.

2. The modulation current to the solenoid is incorrect.

3. The setting of the line relief valve is too low.

4. The spool in the ride control valve and the mating surfaces are worn or damaged.

5. The main control valve spool and/or the mating surfaces are worn or damaged.

6. A solenoid valve for pilot pressure is sticking.

7. A solenoid valve for pilot pressure is receiving low voltage.

8. Maximum current is set too low in the implement configuration screen.

Problem 22: The implements are not functioning.

Probable causes:

1. The switch for the hydraulic lockout is in the LOCKED position.

2. The hydraulic lockout valve for the pilot oil is not functioning properly.

3. The element in a fuse has separated.

4. The pump is worn or damaged.

5. The pressure reducing valve for pilot pressure is not functioning properly.

6. The load sensing signal relief valve setting is too low.

7. The implement electronic control module is not functioning properly.