ISC, ISCe, QSC8.3, ISL, ISLe3, ISLe4 and QSL9 Engines – Coolant Temperature Above Normal – Sudden Overheat

Symptom Tree  t023

This is symptom tree t023
Cause Correction

Electronic fault codes active or high counts of inactive fault codes

Read the fault codes with an electronic service tool. Refer to Section TF in Troubleshooting and Repair Manual, ISB, QSB4.5, QSB5.9, QSB6.7, ISC, QSC8.3, ISL and QSL9 Engines, CM850 Electronic Control System, Bulletin 4021416 or Troubleshooting and Repair Manual, Electronic Control System, ISC, QSC8.3 and ISL Engines, Bulletin 3666271.


Coolant level is below specification

Inspect the engine and cooling system for external coolant leaks. Repair if necessary. Add coolant. Refer to Procedures 008-018 and 008-020.


Fan drive or fan controls are malfunctioning

Check the fan drive and controls. Refer to Procedure 008-027.


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. Maintain a minimum of 384 cm2 [60 in2] or approximately 19.6 x 19.6 cm [7.5 x 7.5 in] of opening at all times.


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 for ISC, QSC8.3 (industrial and marine engines), ISL, and QSL9 industrial engines, or Procedure 008-014 for QSL9 marine keel cooled engines.


Coolant temperature gauge is malfunctioning

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


Sea water cooling system is malfunctioning

Troubleshoot the sea water system. Refer to the Coolant Temperature Above Normal – Sea Water Cooling System symptom tree.


Cooling system hose is collapsed, restricted, or leaking

Inspect the hoses. Refer to Procedure 008-045.


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.


Coolant 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 008-047.


Torque converter cooler or hydraulic oil cooler is malfunctioning

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


Air or combustion gases are entering the cooling system

Check for air or combustion gases in the cooling system. Refer to Procedure 008-020.


Plugged cooling passages in the cylinder head, head gasket, or cylinder block

Pressure-test the cooling system. Refer to Procedure 008-020.


Cooling system component is malfunctioning

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


Cooling system has insufficient capacity

Refer to the OEM service manual.

Last Modified:  29-Jul-2005