3126B and 3126E On-highway Engines Caterpillar

The Engine Control Module (ECM) detects the following conditions:

• The engine has been running for at least 30 seconds.

• The engine coolant temperature is above 99 °C (210 °F).

The inlet air temperature has risen to 90 °C (194 °F).

System Response:

The ECM logs the diagnostic code into permanent memory.

Note: This diagnostic code requires a customer password in order to be cleared.

Test Step 1. Check the Engine's Cooling System

1. Verify that the cooling system is filled to the proper level. If the coolant level is too low, air may be allowed to enter the cooling system. Air in the cooling system will cause a reduction in coolant flow.

2. Check the quality of the coolant. Follow the recommendations in the Operation and Maintenance Manual.

3. Check for air in the cooling system. Air can enter the cooling system from different sources. The most common causes of air in the cooling system are the incorrect filling of the cooling system and combustion gas leakage into the cooling system. Combustion gas can get into the system through internal cracks, a damaged cylinder head, or a damaged cylinder head gasket.

4. Check the cooling system hoses and clamps. Damaged hoses that leak can normally be seen. Hoses that have no visual leaks can soften during operation. The soft areas of the hose can become kinked or crushed during operation. These areas of the hose can restrict the coolant flow. Hoses become soft and/or get cracks after a period of time. The inside of a hose can deteriorate, and the loose particles of the hose can restrict the coolant flow.

5. Check the water pump. A damaged impeller will not pump an adequate amount of coolant through the cooling system. Remove the water pump and the impeller for damage.

6. Check the water temperature regulator. A water temperature regulator that does not open properly can cause engine overheating.

7. If the cooling system for this application is equipped with an expansion tank, check the shunt line for the expansion tank. The shunt line must be below the coolant level in the expansion tank. A restriction of the shunt line from the expansion tank to the inlet of the jacket water pump will cause a reduction in water pump efficiency. A reduction in water pump efficiency will result in low coolant flow.

8. Check the aftercooler for damage and restrictions. A restriction of air flow through the air to air aftercooler can cause overheating. Check for debris or deposits which would prevent the free flow of air through the aftercooler.

9. Check for a restriction in the air inlet system. A restriction of the air that is coming into the engine can cause high cylinder temperatures. High cylinder temperatures cause higher than normal temperatures in the cooling system.

10. Check for a restriction in the exhaust system. A restriction of exhaust gas flow out of the engine can cause high cylinder temperatures.

11. Consider high ambient temperatures. When ambient temperatures are too high for the rating of the cooling system, there is not enough of a temperature difference between the ambient air and coolant temperatures.

12. Consider high altitude operation. The cooling capacity of the cooling system is reduced at higher altitudes. The engine must have a pressurized cooling system that has the capacity that will prevent the coolant from boiling.

13. Check the engine's operating conditions. If the engine is being operated above the rated operating load, the engine lugging can cause an overheating condition. When the engine is running in the lug condition, the fuel rate is increased with no increase in engine speed. The cooling capacity of the engine's cooling system can be overcome by the increased heat of the added fuel. This will cause engine overheating.

Expected Result:

A thorough inspection of the cooling system revealed a problem.

Results:

• OK - There is a problem with the cooling system.

  Repair: Repair the problem. Ensure that the repair eliminates the problem.

  STOP