If an overheating condition in the brake system occurs, the operator will probably become aware of the overheating condition through the AVSpare Monitoring System.
 | |
| Illustration 1 | g00646019 |
(1) Brake oil temperature gauge (2) Action light | |
 | |
| Illustration 2 | g00646021 |
(2) Action light (3) Alert indicator (4) Message area | |
The truck receives a signal from the brake oil temperature sensor. The brake oil temperature sensor is located in the brake cooling return line before the hoist and brake hydraulic tank. Brake oil temperature gauge (1) will display this sensor input.
 | |
| Illustration 3 | g00281171 |
(A) Temperature reading of 110°C (230°F) (B) Temperature reading of 124°C (255°F) | |
Check brake oil temperature gauge (1) regularly. During this test sequence, do not allow the temperature of the brake oil to get hot. This can cause damage to the brakes.
When the oil temperature is too hot for the current conditions, the alert indicator (3) and the action light (2) come on. An event will be displayed in message area (4). If the brake oil is too hot, reduce the load on the machine or slow the machine speed. Also, downshift the transmission to a lower speed. For additional cooling, park the truck in a convenient location. Put the transmission in NEUTRAL, and run the engine at approximately 1500 rpm.
Problem: The oil temperature gauge indicates high temperature, but there are no alarm indicators.
The oil temperature is too hot according to brake oil temperature gauge (1). Action light (2) and the alert indicator (3) are off.
Probable Cause
Look at the events in message area (4). Determine the location of the error in the electrical system. See Schematic, "776D, 77D, and 777D HAA Tractor/Off-Highway Trucks Electrical Schematic". Consult your AVSpare dealer for additional information.
Problem: The oil temperature is normal, but the action light is on.
The oil temperature is within the normal range, but action light (2) is on.
Note: Action light (2) is activated when the oil temperature reaches 124°C (255°F). The action light remains activated until the oil temperature decreases to approximately 110°C (230°F). Therefore, brake oil temperature gauge (1) may indicate a normal oil temperature while the action light is activated.
Probable Cause
Look at the events in message area (4). Determine the location of the error in the electrical system. See Schematic, "776D, 777D, and 777D HAA Tractor/Off-Highway Truck Electrical Schematic". Consult your AVSpare dealer for additional information.
Problem: The oil temperature is hot.
The oil temperature is too hot according to brake oil temperature gauge (1). Action light (2) and the alert indicator (3) are on. Message area (4) displays an event about brake oil temperature.
Probable Cause
The truck is being operated improperly.
Reference: See Operation And Maintenance Manual for the correct operating techniques of the brake and retarder system.
Operate the machine again. Make sure that engine rpm does not drop below 1700 rpm. This ensures that enough oil flows through the brake oil coolers in order to keep the oil at normal operating temperature.
Problem: The oil temperature is hot on a properly operated machine.
The oil temperature is too hot according to brake oil temperature gauge (1). Action light (2) and the alert indicator (3) are still on after the truck is operated correctly. Message area (4) displays an event about the brake oil temperature.
Probable Cause
 | |
| Illustration 4 | g00647917 |
(5) Torque converter scavenge section (6) Torque converter charging pump section (7) Parking brake release pump section (8) Brake cooling pump section | |
 | |
| Illustration 5 | g00915408 |
(9) Brake oil cooler relief valve | |
 | |
| Illustration 6 | g00647902 |
(10) Hoist pump (11) Pump drive | |
- There is a restriction in the oil cooling system. Refer to the air system and brakes Testing and Adjusting, "Brake Cooling Pressure - Check" in order to determine if there is proper brake cooling oil flow.
- The torque converter charging pump section (6) has failed. Refer to Testing and Adjusting, "Hoist, Torque Converter and Brake System Troubleshooting" for the checking procedure.
- The hoist pump (10) has failed. Refer to Testing and Adjusting, "Hoist, Torque Converter and Brake System Troubleshooting" for the checking procedure.
- The brake oil cooler relief valve (9) is set too low. See the Hydraulic System Testing and Adjusting, "Relief Valve (Brake Oil Cooler) - Test and Adjust".