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| Illustration 1 | g00672779 |
(1) Brake oil temperature gauge (2) Action light for the VIMS | |
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| Illustration 2 | g00672790 |
(3) Alert indicator for the VIMS (4) Message area of the VIMS | |
A truck that has a VIMS module receives signals from temperature sensors. At each of the four brakes, there is a temperature sensor that senses the temperature of the oil. Brake oil temperature gauge (1) will display this sensor input.
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| 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 too 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. Also, push down the manual retarder lever all the way in order to cool the oil.
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 indicator on universal gauge (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, SENR1541, "793C Off-Highway Truck Electrical System". Consult your Caterpillar 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, SENR1541, "793C Off-Highway Truck Electrical System". Consult your Caterpillar 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
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| Illustration 4 | g00525930 |
(5) Hoist and front brake cooling gear pump (6) Parking brake release pump section (7) Brake cooling pump section | |
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| Illustration 5 | g00525932 |
(8) Rear brake oil cooler relief valves | |
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| Illustration 6 | g00520333 |
(9) Front brake oil cooler relief valves | |
- 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 front brake cooling diverter valve is not sending oil through the front brake cooling oil cooler when the service brakes or the retarder are used.
- Hoist and front brake cooling gear pump (5), brake cooling pump section (7), or parking brake release pump section (6) has failed. Refer to Testing and Adjusting, "Hoist and Brake System Troubleshooting" for the checking procedure.
- The pressure for rear brake oil cooler relief valves (8) is set too low. See the hydraulic system Testing and Adjusting, "Relief Valve (Brake Oil Cooler) - Test and Adjust".
- The pressure for front 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".