Thermostat Housing

This procedure covers the removal and replacement of the thermostat housing on a 2015 Kia Forte with 1.8L I4 engine, including coolant drainage, housing removal, and proper refilling of the cooling system.

Warnings

Tools required

Parts

• Thermostat housing assembly × 1 — Use OEM specification
• Thermostat housing gasket × 1 — Use OEM specification
• Lower radiator hose clamp (if damaged) × 1 — Use OEM specification

Fluids

• Hyundai/Kia Long Life Coolant (Green) — 7.5 qt

Preparation

1. Ensure engine is completely cold to the touch before beginning work
2. Park vehicle on level ground and engage parking brake
3. Raise and secure front of vehicle on jack stands
4. Remove engine splash shield/lower cover to access drain plug and thermostat housing
5. Place coolant drain pan under radiator drain plug location

Procedure

1. 1

   Drain cooling system
   Locate the radiator drain plug at the bottom of the radiator on the driver's side. Using a 10mm socket, carefully loosen the drain plug and allow coolant to drain completely into the drain pan. Once drained, reinstall the drain plug to the specified torque.
   Torque spec

   Coolant Drain Plug15 Nm (11 lb-ft)
2. 2

   Remove lower radiator hose
   Locate the lower radiator hose connection at the thermostat housing. Using hose clamp pliers or a flathead screwdriver, loosen the hose clamp at the thermostat housing connection. Twist the hose gently to break it free from the housing, then pull it off. Have a rag ready to catch residual coolant.
3. 3

   Disconnect coolant temperature sensor
   Locate the coolant temperature sensor electrical connector on the thermostat housing. Press the locking tab and carefully pull the connector straight off the sensor. Do not pull on the wires.
4. 4

   Remove thermostat housing bolts
   Locate the two or three thermostat housing mounting bolts securing the housing to the engine block. Using a 12mm socket, remove all housing bolts in a criss-cross pattern. Keep bolts organized for reinstallation.
   ℹ️Access to the upper bolt may be limited. A swivel socket or universal joint may be helpful for removal.
5. 5

   Remove thermostat housing
   Carefully pull the thermostat housing away from the engine block. If the housing is stuck, gently tap it with a rubber mallet to break the gasket seal. Do not pry against the sealing surface as this will cause damage requiring machining.
6. 6

   Clean mating surfaces
   Using a plastic gasket scraper, carefully remove all old gasket material from both the engine block mating surface and the thermostat housing mating surface (if reusing). Do not use metal scrapers that could gouge the aluminum surfaces. Clean surfaces thoroughly with a lint-free rag and inspect for damage or warping.
   ⚠Ensure no gasket material or debris falls into the engine coolant passages. Cover openings with clean rags during cleaning.
7. 7

   Install new gasket and thermostat housing
   Position the new gasket onto the engine block mating surface, ensuring proper alignment with the bolt holes and coolant passages. Place the new or cleaned thermostat housing onto the gasket, aligning all bolt holes. Start all housing bolts by hand to ensure proper thread engagement.
8. 8

   Torque thermostat housing bolts
   Using a torque wrench, tighten the thermostat housing bolts in a criss-cross pattern to the specified torque. Make at least two passes, first to approximately 50% torque, then to final torque specification.
   ⚠Over-tightening aluminum housing bolts can strip threads or crack the housing. Use a calibrated torque wrench and do not exceed specified torque.
   Torque spec

   Housing Bolts13 Nm (10 lb-ft)
9. 9

   Reconnect lower radiator hose and sensor
   Slide the lower radiator hose fully onto the thermostat housing connection until it seats against the stop. Position the hose clamp over the connection area and tighten to the specified torque. Reconnect the coolant temperature sensor electrical connector until it clicks into place.
   Torque spec

   Coolant Hose Clamps4 Nm (3 lb-ft)
10. 10

    Refill cooling system
    Reinstall the engine splash shield. Lower the vehicle to the ground. Remove the radiator cap and coolant reservoir cap. Using a funnel, slowly fill the cooling system through the radiator opening with the specified Hyundai/Kia Long Life coolant until full. Fill the coolant reservoir to the MAX line. Leave radiator cap off.
11. 11

    Bleed cooling system
    Start the engine and allow it to idle with the radiator cap off. Turn the heater to maximum heat and fan speed. As the engine warms, the coolant level will drop as the thermostat opens and air is purged. Continue adding coolant as needed to maintain proper level. Run until the cooling fan cycles on and off at least twice, indicating the thermostat is functioning and the system is properly bled.
    ⚠Monitor engine temperature gauge during bleeding process. If temperature rises above normal operating range, shut off engine immediately and allow to cool.
12. 12

    Final fill and cap installation
    With the engine at operating temperature and cooling fan having cycled, shut off the engine. Allow to cool for 10-15 minutes. Top off radiator to the fill neck and coolant reservoir to the MAX line. Install radiator cap securely. Wipe down all connections and check for leaks.

Reassembly

1. Ensure all hose clamps are properly tightened and positioned
2. Verify coolant temperature sensor connector is fully seated and locked
3. Double-check that all thermostat housing bolts are torqued to specification
4. Confirm engine splash shield is reinstalled securely

Verification

• Start engine and visually inspect thermostat housing and all hose connections for coolant leaks while engine warms up
• Verify engine reaches normal operating temperature (thermostat opening properly) by monitoring temperature gauge
• Confirm heater produces hot air when set to maximum temperature
• Check coolant level in reservoir after test drive and top off if necessary to MAX line
• Verify no coolant leaks are present after overnight parking by checking ground under vehicle
• Monitor coolant level over the next few days and top off as needed as air pockets dissipate

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