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| Illustration 1 | g00318003 |
EMS (1) Brake oil temperature gauge (2) Action light (3) Alert indicator for the brakes and the torque converter oil temperature | |
An EMS equipped truck will receive signals for the brake oil temperature gauge (1) and the alert indicator (3) from the torque converter outlet oil.
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.
The alert indicator (3) is on the EMS panel. The EMS action light (2) is located above the speedometer. When the oil temperature is too hot for the current conditions, the alert indicator (3) and the action light (2) come on. If the alert indicator (3) and the action light (2) come on, 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.
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| Illustration 2 | g00452465 |
VIMS (1) Brake oil temperature gauge (2) Action light for the VIMS (3) Alert indicator for the VIMS (4) Message area of the VIMS | |
A truck that has a VIMS module receives signals differently. 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.
The alert indicator (3) is on the VIMS module. Action light (2) is located in the center of the VIMS module above the gauges. 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.
EMS
The oil temperature is too hot according to brake oil temperature gauge (1). Action light (2) and the alert indicator (3) are off.
VIMS
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
EMS
The electrical system is the probable cause. See Schematic, SENR5673, "789B Off-Highway Truck Electrical System".
VIMS
Look at the events in message area (4). Determine the location of the error in the electrical system. See Schematic, SENR8578, "789B Off-Highway Truck with VIMS Electrical System" for a serial number range of 7EK278-370, or see Schematic, SENR1514, "789B Off-Highway Truck with VIMS Electrical System" for a serial number range of 7EK371-up. 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
EMS
The electrical system is the probable cause. See Schematic, SENR5673, "789B Off-Highway Truck Electrical System".
VIMS
Look at the events in message area (4). Determine the location of the error in the electrical system. See Schematic, SENR8578, "789B Off-Highway Truck with VIMS Electrical System" for a serial number range of 7EK278-370, or see Schematic, SENR1514, "789B Off-Highway Truck with VIMS Electrical System" for a serial number range of 7EK371-up. Consult your Caterpillar dealer for additional information.
Problem: The oil temperature is hot.
EMS
The oil temperature is too hot according to brake oil temperature gauge (1). Action light (2) and the alert indicator (3) are on.
VIMS
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.
ReferenceSee 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.
EMS
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.
VIMS
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
There is a restriction in the oil cooling systems.
To determine whether there is a restriction in the cooling system, remove the cover from the brake makeup oil tank of the brake hydraulic system.
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| Illustration 4 | g00285899 |
Typical example of oil flow at low idle | |
Start the engine. Operate the engine in neutral and at low idle. There must be a constant flow of oil from the inlet tube into the brake makeup oil tank.
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| Illustration 5 | g00285901 |
Typical example of oil flow at high idle | |
Increase engine rpm to high idle. The oil flow must increase, as shown.
If oil flow does not match Illustration 4 for low idle and Illustration 5 for high idle, then one of the following causes may be the fault:
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| Illustration 6 | g00483762 |
(5) Rear brake oil cooler relief valve | |
- The hoist and rear brake cooling gear pump or the brake cooling section of the torque converter, parking brake release, and brake cooling gear pump has failed. Refer to Testing and Adjusting, "Hoist, Torque Converter, and Brake System Troubleshooting" for the checking procedure.
- The pressure for the rear brake oil cooler relief valve (5) is set too low. Bench test the rear brake oil cooler relief valve in order to determine whether the pressure setting is correct.
- There is a restriction in the hose assembly from the hydraulic tank to the brake makeup oil tank.