Note: This is not an electronic system problem.
- Radiator fins
- Coolant level
- Radiator cap and/or pressure relief valve
- Coolant temperature gauge
- Restriction in the coolant system
- Water temperature regulator
- Cooling fan
- Coolant pump
- Cylinder head gasket
Check the radiator fins for dirt, debris, and/or damage. Remove any dirt and/or debris and straighten any bent fins.
- Inspect the coolant level. If necessary, add coolant.
- Check the cooling system for leaks. Repair any leaks immediately.
- Pressure test the cooling system. Refer to Testing and Adjusting, "Cooling System" for the correct procedure.
- Check that the seating surfaces of the pressure relief valve and the radiator cap are clean and undamaged.
- Check operation of the pressure relief valve and/or the radiator cap. If necessary, clean the components and/or replace the components.
Compare the reading for the coolant temperature from the electronic service tool to the reading for the coolant temperature from a calibrated test gauge.
- Visually inspect the cooling system for collapsed hoses and/or other restrictions.
- Clean the radiator and flush the radiator. Refer to Testing and Adjusting, "Cooling System".
Check the water temperature regulator for correct operation. Refer to Testing and Adjusting, "Cooling System" for the proper procedure. If necessary, replace the water temperature regulator. Refer to Disassembly and Assembly, "Water Temperature Regulator - Remove and Install" for more information.
- Make sure that the cooling fan is operating correctly. Refer to the troubleshooting guide for the application.
- Check the cooling fan for damage. If necessary, replace the fan. Refer to the service manual for the application.
- Inspect the impeller of the coolant pump for damage and/or erosion.
- Make sure that the drive gear is not loose on the drive shaft of the coolant pump.
- If necessary, replace the coolant pump. Refer to Disassembly and Assembly, "Water Pump - Remove" and Disassembly and Assembly, "Water Pump - Install".
Switch off the engine and allow the engine to cool to below normal working temperature. Remove the pressure cap for the coolant system. Start the engine and inspect the coolant for the presence of bubbles. If bubbles are present in the coolant, combustion gases may be entering the cooling system. Check the cylinder head gasket. Refer to the recommended action for the cylinder head gasket within Troubleshooting, "Coolant in Engine Oil". Check the cylinder head for flatness. Refer to the recommended action for checking flatness of the cylinder head within Systems Operations, "Cylinder Head - Inspect". Fit the pressure cap if there are no bubbles in the coolant.