Kia Rio: Cooling System / Thermostat

Kia Rio 2017-2025 YB Service Manual / Engine Mechanical System / Cooling System / Thermostat

Repair procedures

Removal and Installation

Thermostat

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

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

2.	Disconnect 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.

Install the thermostat with the jiggle valve upward.

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

7.	Start the engine and check for leaks.

8.	Recheck the coolant level.

Heater Pipe

1.	Remove the thermostat.

2.	Disconnect the heater hose (A).

3.	Disconnect the coolant hose (A).

4.	Remove the intake manifold. (Refer to Intake and Exhaust System - "Intake Manifold")

Remove the heater pipe (A).

Tightening torque :

19.6 - 26.5 Nm (2.0 - 2.7 kgf·m, 14.5 - 19.5 lb·ft)

Remove the thermostat housing (A) with O-ring.

Tightening torque :

9.8 - 11.8 Nm (1.0 - 1.2 kgf·m, 7.2 - 8.7 lb·ft)

7.	Install in the reverse order of removal.

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

9.	Start the engine and check for leaks.

10.	Recheck the coolant level.

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.

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

Valve opening temperature : 88 ± 1.5°C (190.4 ± 2.7°F)

Full opening temperature : 100°C (212°F)

Check the valve lift.

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

Valve lift : 8 mm (0.3 in) or more at 95°C (203°F)

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)

•	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 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

•	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.

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