Thermostat Housing

This procedure covers removal and replacement of the thermostat housing on the 2016-2024 Hyundai Tucson with 2.5L I4 AWD engine, including coolant drainage, housing disassembly, gasket replacement, and system refill.

Warnings

Tools required

Parts

• Thermostat housing assembly × 1 — Use OEM specification
• Thermostat housing gasket × 1 — Use OEM specification
• Coolant drain plug washer × 1 — Use OEM specification
• Hose clamps (if damaged) × 2 — Use OEM specification

Fluids

• Hyundai/Kia Long Life Coolant (Green) — 10 qt

Preparation

1. Ensure the engine is completely cool to the touch (at least 2 hours after last operation)
2. Park vehicle on level ground and engage parking brake
3. Remove engine cover by pulling upward on front clips and lifting away
4. Place drain pan underneath radiator drain plug location on driver's side lower radiator tank
5. Gather all replacement parts and verify new thermostat housing includes correct gasket

Procedure

1. 1

   Drain cooling system
   Slowly loosen the radiator cap to release any residual pressure. Remove the radiator cap completely. Locate the coolant drain plug on the lower driver's side of the radiator. Using a 10mm socket, carefully remove the drain plug and allow coolant to drain into the pan. Once drained, inspect the drain plug washer and replace if damaged.
2. 2

   Remove lower radiator hose from thermostat housing
   Locate the lower radiator hose connection point at the thermostat housing on the front-driver's side of the engine block. Using hose clamp pliers or a flat blade screwdriver, loosen the hose clamp and slide it back along the hose approximately 3-4 inches. Twist the hose gently to break the seal, then pull it off the housing nipple. Have a drain pan or towels ready for residual coolant.
3. 3

   Disconnect coolant temperature sensor connector
   Locate the coolant temperature sensor on the thermostat housing. Press the locking tab on the electrical connector and pull it straight off the sensor. Move the wiring harness aside to provide clearance for housing removal.
4. 4

   Remove coolant bypass hose
   Identify the smaller bypass hose connected to the top or side of the thermostat housing. Loosen the hose clamp using a screwdriver or hose clamp pliers and slide it back. Carefully remove the hose from the housing nipple. Note the routing for reinstallation.
5. 5

   Remove thermostat housing mounting bolts
   Using a 12mm socket, remove the thermostat housing mounting bolts in a criss-cross pattern to evenly release tension. There are typically 3-4 bolts securing the housing to the engine block. Keep bolts organized for reinstallation.
6. 6

   Remove thermostat housing assembly
   Carefully pull the thermostat housing away from the engine block. If it resists, gently tap the housing with a plastic mallet or pry carefully with a plastic scraper - do not use metal tools that could damage sealing surfaces. Remove the housing completely and set aside. The thermostat will typically remain in the housing.
7. 7

   Clean gasket 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 housing). Do not use metal scrapers that could gouge the aluminum surfaces. Clean surfaces thoroughly with a clean shop towel and ensure no debris remains in the coolant passages.
   ⚠Ensure no gasket material or debris falls into the engine coolant passages. Contamination can block coolant flow and cause engine overheating.
8. 8

   Install new thermostat housing
   Position the new gasket on the engine block mating surface, ensuring all bolt holes and coolant passages align correctly. The gasket may have alignment pins or tabs. Place the new thermostat housing onto the engine block, ensuring the gasket stays in position. Hand-thread all mounting bolts to prevent cross-threading.
9. 9

   Torque thermostat housing bolts
   Using a torque wrench, tighten the thermostat housing mounting bolts in a criss-cross pattern to the specified torque. Start at the center bolt and work outward to ensure even gasket compression and proper sealing.
   Torque spec

   Housing Bolts14 Nm (10 lb-ft)
10. 10

    Reconnect coolant hoses
    Reconnect the coolant bypass hose to the thermostat housing nipple, ensuring it is fully seated. Position the hose clamp over the connection point and tighten to specification using a torque wrench with appropriate adapter. Reconnect the lower radiator hose in the same manner, ensuring the hose is fully seated on the housing nipple before tightening the clamp.
    Torque spec

    Coolant Hose Clamps4 Nm (3 lb-ft)
11. 11

    Reconnect electrical connector
    Reconnect the coolant temperature sensor electrical connector to the sensor on the new thermostat housing. Ensure the connector locks into place with an audible click.
12. 12

    Install drain plug and refill cooling system
    Install the radiator drain plug with a new washer and torque to specification using a 10mm socket and torque wrench. Fill the cooling system through the radiator cap opening with Hyundai/Kia Long Life Coolant (Green) mixed to the proper concentration. Fill slowly to allow air to escape. Fill until coolant is visible at the radiator neck.
    Torque spec

    Coolant Drain Plug15 Nm (11 lb-ft)
13. 13

    Bleed cooling system
    With the radiator cap still off, start the engine and allow it to idle. Set the heater to maximum temperature and fan speed. As the engine warms, coolant level will drop as air is purged from the system. Add coolant as needed to maintain proper level. Run engine until the thermostat opens (radiator hoses become hot) and the cooling fan cycles on. Continue adding coolant as needed.
    ⚠Monitor engine temperature gauge closely during bleeding procedure. If temperature rises above normal range, shut off engine immediately and allow to cool.
14. 14

    Final coolant level adjustment
    Once the cooling fan has cycled and no more air bubbles emerge from the radiator, top off coolant to the proper level at the radiator neck. Install the radiator cap securely. Check the coolant reservoir and fill to the FULL mark with the same coolant mixture. Reinstall the engine cover.

Reassembly

1. Double-check all hose connections are secure and clamps are properly tightened
2. Verify the coolant temperature sensor connector is fully engaged
3. Ensure engine cover is properly seated on all mounting points
4. Wipe down any coolant spills from engine surfaces and components

Verification

• Start the engine and verify no coolant leaks are present at the thermostat housing, hose connections, or drain plug
• Allow engine to reach normal operating temperature and confirm the temperature gauge reads in the normal range
• Verify the cooling fan operates properly when engine reaches operating temperature
• After the first drive cycle (10-20 miles), recheck coolant level in the reservoir when engine is cool and top off if necessary
• Inspect all connections for leaks after the first few drive cycles and retighten if needed

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