12M, 140, 140M and 160M Motor Graders Braking and Hydraulic Fan System Brake and Hydraulic Fan System Caterpillar

Troubleshooting the Braking and Hydraulic Fan System

Problem: Fan will not spin, or the fan will spin when machine first turned on but stops spinning shortly thereafter

Probable Causes

• The margin pressure setting of the pump is too low. Inadequate margin pressure can cause the priority valve to close. When the priority valve is closed, most oil that flows to the fan motor will be blocked. Adjust the margin to the specified value. Refer to the Testing and Adjusting, "Piston Pump (Brake, Hydraulic Fan) Margin Pressure - Test and Adjust" in order to set the margin pressure of the pump.

Problem: Fan spins when machine is cold, but stops when machine gets warm or gets hot

Probable Causes

• The margin pressure setting of the pump is incorrect. The margin pressure can change slightly as the hydraulic oil warms up. Adjust all margin pressure settings with warm oil 62.5° ± 2.5°C (145° ± 5°F). There is not much allowance in this system between the margin pressure and the priority valve, so the margin pressure setting of the pump must be fairly accurate. Refer to the Testing and Adjusting, "Piston Pump (Brake, Hydraulic Fan) Margin Pressure - Test and Adjust" in order to set the margin pressure of the pump.

Problem: Fan spins at or near maximum fan speed when maximum speed is not required

Probable Causes

• The fan speed solenoid failed or the fan speed solenoid is not getting current.

• The brake circuit stuck in constant charging. Refer to section "When the engine is idling and the brakes are not applied, the brake accumulators seem to drain down and the pump enters the charge cycle at a rate of less than one minute per cycle." for probable causes.

• The high-pressure cutoff setting of the pump is too low. If the high-pressure cutoff setting is below the cutout setting of the charging valve, the brakes will never reach the cutout pressure. The priority valve will never shift flow back to the fan. Adjust high-pressure cutoff to the specified value. Refer to the Testing and Adjusting, "Piston Pump (Brake, Hydraulic Fan) High Pressure Stall - Test and Adjust" in order to set the high-pressure cutoff of the pump.

Problem: The calibration in AVSpare Electronic Technician (ET) cannot achieve minimum desired fan speed, the lowest fan speed possible is higher than 550 ± 50 rpm

Probable Causes

• The pump margin pressure setting is too high. Although Cat ET is used to set the actual current value to the fan solenoid in order to achieve the desired fan speed, the margin and the high-pressure cutoff settings must be properly set in order to allow Cat ET to achieve the range of desired fan speeds. Refer to the Testing and Adjusting, "Piston Pump (Brake, Hydraulic Fan) Margin Pressure - Test and Adjust" in order to set the margin pressure of the pump. Refer to the Testing and Adjusting, "Piston Pump (Brake, Hydraulic Fan) High Pressure Stall - Test and Adjust" in order to set the high-pressure cutoff of the pump. Refer to the Testing and Adjusting, "Hydraulic Fan Speed - Calibrate and Adjust" in order to set the fan speed.

Problem: Maximum fan speed is not attainable

Probable Causes

• The fan speed solenoid is not operating properly.

• Pump cutoff pressure is too low. Refer to the Testing and Adjusting, "Piston Pump (Brake, Hydraulic Fan) High Pressure Stall - Test and Adjust" in order to set the high-pressure cutoff of the pump.

• The piston pump is damaged or worn.

Problem: Fan makes noise, especially when the brakes are charging

Probable Causes

• The motor is operating incorrectly or the motor is damaged.

Problem: Only get one or two applications of brake pedal between brake valve cut out and brake valve cut in

Probable Causes

• The cut out valve is not set correctly.

• The cut-in valve is not set correctly.

• The precharge of the brake accumulator is incorrect. Refer to Testing and Adjusting, "Brake Accumulator (Service) - Test and Charge" for the procedure to set the precharge of the brake accumulator.

• The seals on the brake piston have failed.

Problem: When the engine is idling and the brakes are not applied, the brake accumulators seem to drain down and the pump enters the charge cycle at a rate of less than one minute per cycle

Probable Causes

• The cut out valve is not set correctly.

• Check the service brake control valve for leakage. Refer to Testing and Adjusting, "Brake Control Valve (Service) - Check" in order to check the internal leakage of the brake control valve.

• Check for leaks around fan and brake block

• Check for leaks around brake accumulators.

Problem: The wheels rotate, the engine does not stall, and the brake circuit has no leakage during the service brake test

Probable Causes

• The brake linings for the service brakes are worn. Refer to , "Brake Disc Wear - Check" portion of this book.

• Piston seals are damaged or broken.

Problem: The service brakes are noisy when stopping the machine

• Hydraulic Oil Additive was not added to the tandems during the refill. Refer to the Operation and Maintenance Manual, "Capacities Refill" or the Operation and Maintenance Manual, "Lubricant Viscosities" for information regarding the addition of this Hydraulic Oil Additive .

• Service brakes are worn or damaged.

Problem: The parking brake does not hold the machine stationary.

Refer to the Power Train Systems Operation/Testing and Adjusting for information regarding the parking brake and parking brake components for your machine.

Problem: The parking brake does not engage when the parking brake switch is actuated

Refer to the Power Train Systems Operation/Testing and Adjusting for information regarding the parking brake and parking brake components for your machine.