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

Warnings

Tools required

Parts

• Coolant temperature sensor × 1 — Use OEM specification
• Coolant temperature sensor O-ring × 1 — Usually included with sensor

Fluids

• Hyundai/Kia Long Life Coolant (Green) — 2 qt

Preparation

1. Ensure engine is completely cold to the touch
2. Park vehicle on level ground and engage parking brake
3. Place drain pan under radiator drain plug location at bottom of radiator
4. Remove engine cover by pulling upward on front clips and lifting off

Procedure

1. 1

   Drain coolant from system
   Slowly turn the radiator cap counterclockwise to release any residual pressure, then remove completely. Locate the coolant drain plug at the bottom driver's side of the radiator. Open the drain plug and allow coolant to drain into the pan. You only need to drain until coolant level is below the sensor location on the thermostat housing.
   Torque spec

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

   Disconnect sensor electrical connector
   Locate the coolant temperature sensor on the thermostat housing at the front of the engine, driver's side near the cylinder head. Press down on the locking tab of the electrical connector and pull the connector straight off the sensor. Move the wiring harness aside.
   ⚠Do not pull on the wiring; press the tab and pull only on the connector body to avoid damaging the wiring.
3. 3

   Remove coolant temperature sensor
   Using a 19mm deep socket with ratchet and extension, turn the coolant temperature sensor counterclockwise to remove it from the thermostat housing. Some residual coolant will drain out as the sensor is removed. Have a shop towel ready to catch drips. Inspect the old sensor O-ring for damage.
   ℹ️The sensor may be tight from heat cycling. Do not use excessive force that could damage the thermostat housing threads.
4. 4

   Prepare sensor mounting location
   Inspect the sensor mounting hole threads in the thermostat housing. Use a wire brush to clean any corrosion or debris from the threads if necessary. Wipe the area clean with a shop towel. Ensure the sealing surface around the threads is clean and free of old O-ring material.
   ⚠Do not allow debris to fall into the coolant passage during cleaning.
5. 5

   Install new coolant temperature sensor
   Verify the new sensor has a new O-ring properly seated in its groove. Insert the sensor into the thermostat housing and hand-tighten clockwise. Once seated, use the 19mm deep socket to snug the sensor. Tighten to finger-tight plus 1/8 to 1/4 turn. Do not over-tighten as the O-ring provides the seal.
   ⚠Over-tightening can crack the sensor body or damage the thermostat housing threads. The sensor does not require high torque; the O-ring creates the seal.
6. 6

   Reconnect electrical connector
   Push the electrical connector straight onto the coolant temperature sensor until you hear and feel a positive click. Gently tug on the connector to verify it is fully locked in place.
7. 7

   Close drain and refill cooling system
   Close and tighten the radiator drain plug. Slowly pour Hyundai/Kia Long Life Coolant (Green) into the radiator until the level reaches the radiator neck. Pour additional coolant into the coolant reservoir until it reaches the MAX mark. Start the engine and allow it to warm up to operating temperature with the radiator cap off. Add coolant as needed as air purges from the system.
   ⚠Keep the coolant level above the radiator core during warm-up to prevent air pockets. Add coolant gradually as the level drops.
   Torque spec

   Coolant Drain Plug15 Nm (11 lb-ft)
8. 8

   Bleed cooling system
   With the engine at operating temperature and heater set to maximum heat, observe coolant circulation in the radiator. Gently squeeze the upper radiator hose several times to help release trapped air. Continue adding coolant as necessary. Once the coolant level stabilizes and no more air bubbles appear, turn off the engine and allow it to cool for 15 minutes.
   ⚠Be careful of cooling fan operation during this process. The fan can engage at any time when the engine is running.
9. 9

   Final coolant level check
   After the engine has cooled for 15 minutes, check the radiator coolant level and top off if needed to the radiator neck. Check the coolant reservoir and ensure level is at the MAX mark. Install the radiator cap by turning clockwise until it clicks into the locked position. Reinstall the engine cover.

Reassembly

1. Ensure all electrical connectors are fully seated and locked
2. Verify radiator drain plug is properly tightened and not leaking
3. Confirm coolant reservoir is filled to MAX mark
4. Reinstall engine cover securely

Verification

• Start the engine and verify no coolant leaks from the sensor location
• Allow engine to reach operating temperature and verify temperature gauge reads normally
• Use a scan tool to verify coolant temperature sensor reads between 180-220°F at operating temperature
• Check for any diagnostic trouble codes related to the coolant temperature sensor
• Recheck coolant level in reservoir after first drive cycle and top off if necessary

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