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

Symptom Tree  t024

This is symptom tree t024
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 temperature gauge or sensor is malfunctioning

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


Excessive coolant flow through OEM plumbing and heater cores

Close valves to heater cores. Run engine. If engine operates at normal temperature, refer to the OEM service manual.


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


Engine is operating at low ambient temperature

Check the winterfront, shutters, and under-the-hood air. Use under-the-hood intake air in cold weather. Refer to the OEM service manual.


Fan drive or fan controls are malfunctioning

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


Cooling system component is malfunctioning

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


Engine idle time is excessive

Low oil and coolant temperatures can be caused by long idle time (greater than 10 minutes). Shut off the engine rather than idle for long periods. If idle time is necessary, raise the idle speed. Procedure 008-020

Last Modified:  20-Jun-2005