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

Warnings

Tools required

Parts

• Thermostat assembly with gasket × 1 — Use OEM Hyundai part
• Coolant hose clamps (if damaged) × 2 — Replace as needed
• O-ring seal for thermostat housing × 1 — Usually included with thermostat

Fluids

• Hyundai/Kia Long Life Coolant (Green) — 5 qt

Preparation

1. Ensure engine is completely cold (at least 2 hours after last operation)
2. Park vehicle on level ground and apply parking brake
3. Locate the thermostat housing on the front of the engine block, below the intake manifold on the passenger side
4. Place drain pan under the radiator drain plug located at the bottom of the radiator
5. Have approximately 5 quarts of fresh Hyundai/Kia Long Life Coolant ready for refill

Procedure

1. 1

   Drain cooling system
   Slowly loosen the radiator cap to release any residual pressure. Open the radiator drain plug at the bottom of the radiator and drain coolant into the drain pan. If necessary, open the bleed screw on the thermostat housing to improve drainage. Once drained, close the radiator drain plug.
2. 2

   Remove engine cover if equipped
   If your Tucson has a plastic engine cover, pull upward firmly on the cover to release the mounting clips. Set aside.
3. 3

   Disconnect coolant hoses from thermostat housing
   Locate the upper and lower coolant hoses connected to the thermostat housing. Using a flathead screwdriver, loosen the hose clamps on both hoses. Twist the hoses gently to break the seal, then pull them off the thermostat housing. Have a shop towel ready as residual coolant will drain out.
4. 4

   Disconnect coolant temperature sensor
   Locate the coolant temperature sensor on the thermostat housing. Press the tab on the electrical connector and pull it straight off the sensor. If the sensor will be reused, leave it installed in the housing.
   Torque spec

   Coolant Temperature Sensor20 Nm (15 lb-ft)
5. 5

   Remove thermostat housing bolts
   Using a 10mm or 12mm socket (verify which fits your specific housing), remove the thermostat housing bolts in a crisscross pattern. There are typically 3-4 bolts securing the housing to the engine block. Keep track of bolt locations as they may be different lengths.
   Torque spec

   Thermostat Housing Bolts15 Nm (11 lb-ft)
6. 6

   Remove thermostat housing and old thermostat
   Carefully pull the thermostat housing away from the engine block. The thermostat will either be in the housing or seated in the engine block recess. Remove the old thermostat and note its orientation with the spring side facing toward the engine block. Remove and discard the old O-ring seal.
   ℹ️The thermostat jiggle valve (small hole or pin) must be positioned at the top when installed to allow air to escape during filling.
7. 7

   Clean mating surfaces
   Using a plastic scraper, carefully clean all old gasket material and residue from both the thermostat housing and the engine block mating surface. Ensure surfaces are completely clean and dry. Do not use metal scrapers that could damage the aluminum surfaces.
   ⚠Scratches or gouges in the mating surfaces will cause coolant leaks. Work carefully with plastic tools only.
   Torque spec

   Thermostat Housing Bolts15 Nm (11 lb-ft)
8. 8

   Install new thermostat
   Install the new O-ring seal into the groove on the thermostat or housing (depending on design). Position the new thermostat in the engine block recess with the spring side facing the engine block and the jiggle valve positioned at the 12 o'clock (top) position. Verify the thermostat seats fully in the recess.
9. 9

   Reinstall thermostat housing
   Position the thermostat housing over the thermostat, ensuring it aligns properly with the dowel pins if equipped. Hand-thread all housing bolts first to ensure proper alignment. Tighten the bolts in a crisscross pattern to the specified torque of 14.0 Nm (10 lb-ft) using a torque wrench.
   Torque spec

   Thermostat Housing Bolts15 Nm (11 lb-ft)
10. 10

    Reconnect coolant temperature sensor
    If the coolant temperature sensor was removed, apply a thin coating of thread sealant to the threads and install it into the thermostat housing, torquing to 20.0 Nm (15 lb-ft). Reconnect the electrical connector until it clicks into place.
    Torque spec

    Coolant Temperature Sensor20 Nm (15 lb-ft)
11. 11

    Reconnect coolant hoses
    Slide the coolant hoses back onto the thermostat housing fittings, pushing them fully onto the barbs. Position the hose clamps over the connection points and tighten to 4.0 Nm (3.0 lb-ft). Ensure hoses are routed properly without kinks.
12. 12

    Fill and bleed cooling system
    Open the bleed screw on top of the thermostat housing approximately 2-3 turns. Slowly fill the cooling system through the radiator cap opening with fresh Hyundai/Kia Long Life Coolant until coolant flows from the bleed screw without air bubbles. Close the bleed screw to 7.0 Nm (5.0 lb-ft). Continue filling the radiator to the proper level, then fill the coolant reservoir to the FULL mark. Install the radiator cap.
    ℹ️Fill slowly to avoid trapping air pockets in the system. The bleed screw allows air to escape as the system fills.
13. 13

    Run engine and complete bleeding
    Start the engine and let it idle with the heater set to maximum heat. Monitor the temperature gauge and watch for coolant circulation. Allow the engine to reach normal operating temperature (thermostat opens around 180-190°F). Check for leaks around the thermostat housing and hoses. Once at operating temperature, rev the engine to 2500-3000 RPM 3-4 times to purge remaining air. Turn off the engine and allow to cool.
    ⚠Monitor the temperature gauge closely during first startup. If the gauge shows overheating, shut off the engine immediately and recheck the installation.
14. 14

    Verify coolant level and recheck for leaks
    Once the engine has cooled, recheck the coolant level in both the radiator and reservoir. Top off as necessary. Inspect all connections at the thermostat housing, hoses, and bleed screw for any signs of leakage. Reinstall the engine cover if equipped.

Reassembly

1. Ensure all hose clamps are properly tightened and positioned
2. Verify the coolant temperature sensor connector is fully seated and locked
3. Double-check that the bleed screw is closed and torqued properly
4. Reinstall engine cover by aligning clips and pressing down firmly

Verification

• Start the engine and verify normal temperature gauge operation (should reach middle range within 5-10 minutes)
• Confirm heat output from cabin heater is strong and consistent
• Check for any coolant leaks around thermostat housing, hoses, and bleed screw after engine reaches operating temperature
• Verify coolant level remains stable in the reservoir after several heat cycles
• Test drive the vehicle and monitor temperature gauge for stable operation under load
• Use a coolant hydrometer or refractometer to verify proper coolant concentration (typically 50/50 mix for proper freeze protection)

More procedures for this vehicle