Kia Forte: Cooling System / Thermostat

Kia Forte 2019-2025 (BD) Service Manual / Engine Mechanical System / Cooling System / Thermostat

Components and components location

Components

1. Water inlet fitting

2. Thermostat

Repair procedures

Removal

Disassembly of the thermostat would have an adverse effect, causing a lowering of cooling efficiency.

1.	Drain the engine coolant. (Refer to Cooling System - "Coolant")

2.	Remove the radiator lower hose (A).

Remove the water inlet fitting (A).

Tightening torque :

18.6 - 23.5 N·m (1.9 - 2.4 kgf·m, 13.7 - 17.4 lb·ft)

4.	Remove the thermostat (A).

Install in the reverse order of removal.

Place the thermostat with the jiggle valve (A) upward.

6.	Fill with the engine coolant. (Refer to Cooling System - "Coolant")

7.	Start engine and check for leaks.

Inspection

Immerse thermostat in water heated to over 95°C (203°F), then heat for at least 3 minutes to check valve lift.

•	Do not use water below 95°C (203°F).

•	Do not directly heat unit as this will damage thermostat.

Check the valve opening temperature.

Valve opening temperature :

82±1.5°C (179.6 ± 2.7°F)

Full opening temperature :

95°C (203°F)

If the valve opening temperature is not as specified, replace the thermostat.

Check the valve lift.

Valve lift : 8 mm (0.3 in.) or more at 100°C (212°F)

If the valve lift is not as specified, replace the thermostat.

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 blowed-out)

•	Temperature gauge indicates 'LOW'

Visually check after removing the radiator cap.

•	Insufficient coolant or leakage.

•	After refilling coolant, recheck.

KDS check&Starting engine

•	Check DTCs

•	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.

•	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

•	Temperature gauge 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.

KDS 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.

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