6.7L Cummins Troubleshooting – Coolant Temperature Above Normal – Sudden Overheat

Electronic fault codes active or high counts of inactive fault codes

View and troubleshoot the fault codes with INSITEtu. Refer to the Troubleshooting and Repair Manual, CM21 00 and CM2150 Electronic Control System, Bulletin 4021570.

Coolant level is below specification

Check the coolant level. Check for an external leak. Refer to Procedure 008-018 and Procedure 008-020 and the Coolant Leak External Symptom Tree . Sample the lubricating oil and have a laboratory check for coolant in the oil (internal eak).

Fan drive belt is broken or loose

Check the fan drive belt. Replace the belt if necessary. Refer to Procedure 008-002.

Cold weather radiator cover or winterfront is closed

Open the cold weather radiator cover or the winterfront. Refer to the OEM Service Manual

Radiator shutters are not opening completely, or the shutterstat setting is wrong

Inspect the radiator shutters. Repair or replace if necessary. Check the shutterstat setting. Refer to
the OEM service manual.

Charge air cooler fins, radiator fins, or air conditioner condenser fins are damaged or obstructed with debris

Inspect the charge air cooler, air conditioner condenser, and radiator fins. Clean, if necessary.
Refer to Procedure 010-027.

Thermostat is not correct or is malfunctioning

Check the thermostat for the correct part number and for correct operation. Refer to Procedure
008-013.

Coolant temperature gauge is malfunctioning

Test the temperature gauge. Repair or replace the gauge, if necessary. Refer to the OEM service
manual.

Coolant temperature gauge or sensor is malfunctioning

Test the gauge and the sensor. Repair or replace, if necessary. Refer to the OEM service manual
instructions on troubleshooting the gauge. Refer to the Troubleshooting and Repair Manual, CM2100 and CM2150 Electronic Control System, Bulletin 4021570, to monitor and check the coolant temperature sensor.

Cooling system hose is collapsed, restricted, or leaking

Inspect the hoses. Refer to Procedure 008-020.

Fill line or vent lines are restricted, obstructed, or not routed correctly

Check the vent lines and the fill line for correct routing and for restriction. Refer to the OEM
service manual.

Water pump is malfunctioning

Check the water pump for correct operation. Replace the water pump if necessary. Refer to Procedure 008-062.

Radiator cap is not correct, is malfunctioning, or has low-pressure rating

Check the radiator pressure cap. Refer to Procedure 008-020.

Fan drive or fan controls are malfunctioning

Check the fan drive and controls. Refer to Procedure 008-026 if electronically controlled by he engine’s ECM. If OEM controlled, refer to the OEM service manual.

Cooling system component is malfunctioning

Perform the cooling system diagnostics test. Refer to Procedure 008-020.

Torque converter cooler or hydraulic oil cooler is malfunctioning

Remove and inspect the cooler cores and a-rings. Refer to the OEM service manual.