12M, 140, 140M, 150, 160M and 160 Motor Graders Hydraulic and Steering System Hydraulic and Steering System Caterpillar

Problem: The temperature of the oil is too hot.

Probable Cause

• The viscosity of the oil is incorrect.

• The signal relief valve is set too high. Refer to Testing and Adjusting, "Pump Control Valve (Implement, Steering) - Test and Adjust".

• The implement relief valve is set too low. Refer to Testing and Adjusting, "Pump Control Valve (Implement, Steering) - Test and Adjust".

• The implement and steering pump has too much wear (high leakage).

• There is a restriction in an oil passage.

• The load of the system is too high.

• The signal purge valve has malfunctioned. The signal purge valve is in the pump control valve. The signal purge valve should be in the CLOSED position.

• There is air in the oil.

• Outside air temperature is too hot.

Problem: The implement and steering pump makes unusual noise. The cylinder rods do not move evenly. Air bubbles are in the oil.

Probable Cause

• There is a leak in the oil line between the hydraulic tank and the implement and steering pump.

• There is a leak in the oil line between the hydraulic tank and the hydraulic fan pump.

• The hydraulic system was not purged correctly. The system may not have been purged correctly after assembly of the hydraulic system. The system may not have been purged correctly after inspection of the hydraulic system, or after testing of the hydraulic system. Refer to Testing and Adjusting, "Steering System - Purge".

• The relief valve constantly cycles.

• There is leakage around the cylinder seals.

• The operator is using the blade float function in order to drop the blade.

Problem: The maximum pressure of the implement and steering pump is too low.

Probable Cause

• The signal relief valve is set too low.

• There is a leak in the signal network or there is a restriction in the signal network.

• The pump control valve is set incorrectly. Refer to Testing and Adjusting, "Pump Control Valve (Implement, Steering) - Test and Adjust".

• The margin pressure is set too low.

• The implement and steering pump is not upstroking. The swashplate is blocked.

Problem: The pressure of the implement and steering pump is too high.

Probable Cause

• The signal relief valve is set too high. Refer to Testing and Adjusting, "Pump Control Valve (Implement, Steering) - Test and Adjust".

• The margin pressure is set too high.

• The implement and steering pump is not destroking. The actuator piston is stuck or the swashplate is blocked.

Problem: The implement and steering pump has no pressure.

Probable Cause

• The hydraulic system is low on oil.

• The implement and steering pump has malfunctioned or the pump drive shaft has malfunctioned.

• The pump control valve is set incorrectly.

• The check valve at the pump discharge line is possible stuck.

Problem: The implement and steering pump remains at margin pressure. When the implements are used or the steering is used, the pump will not upstroke.

Probable Cause

• The implement and steering pump is not receiving a signal.

• The pump control valve is not working.

• The implement and steering pump is not upstroking. The swashplate is blocked.

Problem: The front wheels vibrate, when you steer the machine.

Probable Cause

• Air is in the steering cylinders and air is in the steering system. Refer to Testing and Adjusting, "Steering System - Purge".

• Check the steering priority valve that is in the steering control valve.

Problem: The steering does not work but the implements do work.

Probable Cause

• The shuttle valve in the pump signal line is faulty.

• The steering priority valve is malfunctioning. The pressure from the implement and steering pump is blocked to the steering circuit.

• There is blockage or damage to the steering circuit or components.

Problem: The response of one implement is too slow.

Probable Cause

• The valve spool that is installed in the control valve is incorrect for the implement.

• The signal check valve in the signal network is functioning incorrectly.

• The implement control valve has failed.

• The implement relief valve is set too low.

• The signal relief valve is set too low.

Problem: The response of all the implements are too slow.

Probable Cause

• The check valve is leaking or the ball resolver in the signal network system is leaking.

• There is contamination in any of the control valves.

• Air is in the system.

• The signal purge valve is stuck open.

• The signal relief valve malfunctions.

• The flow compensator (margin pressure) is set improperly.

• The implement relief valve is set too low or the implement relief valve leaks.

• The steering priority valve has malfunctioned.

Problem: Implement circuits will not operate when one cylinder is stalled.

Probable Cause

• The pressure compensator (pressure cutoff) is set too low or the signal relief valve is set too high. Refer to Testing and Adjusting, "Pump Control Valve (Implement, Steering) - Test and Adjust".

Problem: The performance of a single implement circuit is erratic.

Probable Cause

• The implement control valve is contaminated.

• The control valve stem is incorrect for this circuit.

• The flow compensator (margin pressure) is set incorrectly.

Problem: The performance of all the implement circuits are erratic.

Probable Cause

• The hydraulic oil in the hydraulic system has not reached normal operating temperature.

• The implement and steering pump has failed or the pump control valve has failed.

• Air is in the hydraulic system.

Problem: Any implement moves with the joystick in the HOLD position.

Probable Cause

• The cylinder piston seals have failed or the cylinder piston seals are worn. The steering line relief valve has failed or the steering line relief valve is worn.

• The lock check valve has failed or the port relief has failed.

• The implement relief valve is malfunctioning.

Problem: When the implement is first activated, the implement surges.

Probable Cause

• An incorrect control stem is installed in the implement control valve.

• Air is in the circuit.

• The flow compensator (margin pressure) is set too high.

Problem: The implements do not work but the steering does work.

Probable Cause

• The shuttle valve has a failed in the signal network.

• The steering priority valve is stuck. The flow of oil to the implements will be stopped.

• The signal relief valve has failed in the OPEN position or the pressure setting is set incorrectly.

• Implement lockout switch is active

• Implement solenoids are out of calibration

Problem: The response of the implements is too fast.

Probable Cause

• An incorrect control stem is installed in the implement control valve.

• The implement control valve has failed.

• The flow compensator (margin pressure) is set too high.

• Implement solenoids are out of calibration

Problem: The implement and steering pump does not return to the low margin pressure after the implement is used.

Probable Cause

• The joystick has interference. The joystick does not return to the HOLD position. The signal pressure is still sent to the pump control valve.

• The signal purge valve has malfunctioned in the CLOSED position.

• The implement and steering pump has failed or the pump control valve has failed.

Problem: When you steer the machine, the implements slow down or the implements stop.

Probable Cause

• The low margin pressure of the implement and steering pump is set low.

• The implement and steering pump has insufficient flow.

Problem: The blade float will not work.

Probable Cause

• The implement control valve has an incorrect control stem.

• There is leakage in the signal network.

• The implement control valve has an incorrect lock valve piston.

• The signal purge valve malfunctions.

• There is contamination in the control stem of the blade lift control valve.

• The viscosity of the oil is incorrect.

• The implement relief valve opens at low oil pressure.

• There is a loose oil line connection on the inlet side of the implement and steering pump. Oil aeration.

• The implement and steering pump has too much wear.

• The operator is using the blade float function in order to drop the blade.

Problem: One or more of the implement cylinders are drifting

Probable Cause

• There are contaminant particles in the hydraulic oil and on the lock and relief valves, preventing a complete seal.

Solution

• Flush hydraulic oil through the affected circuit by operating the implement at high idle for 30 to 60 seconds.

• Cycle the implement a few times during the exercise to dislodge and push any contaminants or particles away from relief valves. Make sure that the implement cylinders reach full extension and retraction during each cycle. The exercise should push particles and contaminants into the hydraulic oil filtration system.