Kia Optima: Thermostat. Troubleshooting - Engine Mechanical System - Kia Optima TF 2011-2026 Service ManualKia Optima: Thermostat. Troubleshooting

Troubleshooting

 
Symptoms
Possible Causes
Remedy
Coolant leakage
• From the thermostat gasket
Check the mounting bolts
• Check the torque of the mounting bolts
• Retighten the bolts and check leakage again.
Check the gasket for damage
• Check gasket or seal for damage
• Replace gaskets and reuse the thermostat.
Cooled excessively
• Low heater performance (cool air blows-out)
• Thermogauge indicates 'LOW'
Visually check after removing the radiator cap.
• Insufficient coolant or leakage.
• After refilling coolant, recheck.
GDS check&Starting engine
• Check DTCs
• Check the fan motor performance as temperature varies.
• Check connection of the fan clutch or the fan motor.
※ If the fan clutch is always connected, there will be a noise at idle.
• Check the engine coolant sensor, wiring and connectors.
• Check the fan motor, the relay and the connector.
• Replace the componants.
Remove the thermostat and inspect
• Check if there are dusts or chips in the thermostat valve.
• Check adherence of the thermostat.
• Clean the thermostat valve and reuse the thermostat.
• Replace the thermostat, if it doesn't work properly.
Heated excessively
• Engine overheated
• Thermogauge indicates 'HI'
Visually check after removing the radiator cap.
• Insufficient coolant or leakage.

※ Be careful when removing a radiator cap of the overheated vehicle.

• Check air in cooling system.
• After refilling coolant, recheck.
• Check the cylinder head gaskets for damage and the tightening torque of the mounting bolts.
GDS check&Starting engine
• Check DTCs
• Check the fan motor performance as temperature varies.
• Check if the fan clutch slips.
• Check the water pump adherence or impeller damaged.
• Check the engine coolant sensor, wiring and connectors.
• Check the fan motor, the relay and the connector.
• Replace the fan clutch, if it doesn't work properly.
• Replace the water pump, if it doesn't work properly.
Immerse the thermostat in boiling water and inspection.
• After removing the thermostat, check it works properly.
※ Check the thermostat opens at the valve opening temperature.
• Replace the thermostat, if it doesn't work properly.


Inspection
1. Immerse the thermostat in water and gradually heat the water. 2. Check the valve opening temperature. Valve opening temperature: 82 ± 1.5°C ( ...

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