Kia Optima Hybrid: Cooling System / Thermostat Troubleshooting

Kia Optima Hybrid (TF HEV) 2016-2020 Service Manual / Engine Mechanical System / Cooling System / 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.

Thermostat Repair procedures

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