- High ambient temperature and/or high inlet air temperature
- Low coolant level and/or coolant leakage
- Insufficient flow of air or coolant through the radiator or heat exchanger
- Faulty water temperature regulators
- Faulty coolant temperature sensor and/or circuit
- Insufficient flow of coolant through the engine
- Exhaust restriction
- Excessive load
- Incorrect base timing
- Incorrect air/fuel ratio
High Ambient Temperature and/or High Inlet Air Temperature
Determine if the ambient air temperature is within the design specifications for the cooling system.
Check for high inlet air temperature. Refer to Troubleshooting, "Inlet Air Temperature (High)".
Determine the cause of the high air temperature. Make corrections, when possible.
Low Coolant Level and/or Coolant Leakage
Note: Low coolant level can be the effect of overheating rather than the cause.
Check the coolant level.
Run the engine to operating temperature. Inspect the cooling system for leaks.
Determine whether the leak occurs before the engine overheats.
Add coolant, if necessary. If leaking is found, make the necessary repairs.
Insufficient Flow of Air and of Coolant Through the Radiator or Heat Exchanger
Check the fins of the radiator for obstructions. Check the fan for proper operation.
If the radiator fins are obstructed, clean the fins. If the fan does not operate properly, make the necessary repairs.
Check for sufficient flow and temperature of the cooling water through the heat exchanger. If the flow of cooling water through the heat exchanger is insufficient, determine the location of the obstruction. If the temperature of the cooling water is too high, determine the cause. Make the necessary repairs.
Check the water temperature regulators for proper operation. Refer to Systems Operation/Testing and Adjusting, "Testing the Cooling System".
Replace the water temperature regulators, if necessary.
Coolant Temperature Sensor and/or Circuit
Check the reading of the coolant temperature on the Caterpillar Electronic Technician (ET). The temperature should rise steadily as the engine is warmed. Ensure that the temperature is reasonable.
If the reading on Cat ET for the coolant temperature is not reasonable, troubleshoot the circuit and the coolant temperature sensor. Refer to Troubleshooting, "Analog Sensor Signal".
Insufficient Flow of Coolant Through the Engine
During normal operation, check the status of the following components:
- Switch for the inlet pressure of the jacket water
- Sensor for the outlet pressure of the jacket water
If the flow of coolant through the engine is not sufficient, determine the cause of the obstruction. Make necessary repairs.
Check the back pressure of the exhaust system. Refer to Systems Operation/Testing and Adjusting, "Restriction of Air Inlet and Exhaust".
If the back pressure exceeds the specifications for the engine, determine the cause of the excessive back pressure. Make the necessary repairs.
Ensure that the load is not excessive. Reduce the load. If necessary, disengage the driven equipment and test the engine.
Verify that the base timing is correct. Refer to Systems Operation/Testing and Adjusting, "Ignition Timing - Adjust".
Incorrect Air/Fuel Ratio (Oxygen Feedback)
An air/fuel mixture that is too rich will cause overheating. Verify that the exhaust emissions are correct. Refer to Systems Operation/Testing and Adjusting, "Air/Fuel Ratio Control - Adjust (Oxygen Feedback)".
A change in the fuel energy content will change the air/fuel ratio. Obtain a fuel analysis.
The fuel supply pressure must be adequate and stable.
Tap on the gas pressure regulator with a soft hammer. If the engine speed changes, inspect the internal parts of the gas pressure regulator for wear. Inspect the gas pressure regulator's diaphragm for leaks. Make sure that the valve moves freely. The valve must seat correctly.
Ensure that the fuel metering valve is operating correctly.
Incorrect Air/Fuel Ratio (NOX Feedback)
An air/fuel mixture that is too rich will cause overheating. Verify that the exhaust emissions are correct. Refer to Systems Operation/Testing and Adjusting, "Air/Fuel Ratio Control - Adjust (NOX Feedback)".
A change in the fuel energy content will change the air/fuel ratio. Obtain a fuel analysis.
The fuel supply pressure must be adequate and stable.
Tap on the gas pressure regulator with a soft hammer. If the engine speed changes, inspect the internal parts of the gas pressure regulator for wear. Inspect the gas pressure regulator's diaphragm for leaks. Check that the valve moves freely. The valve must seat correctly.
Ensure that the fuel metering valve is operating correctly.