Replace the coolant temperature sensor on the 3.5L EcoBoost engine to restore proper temperature monitoring and engine management function.

Warnings

Tools required

Parts

• Coolant temperature sensor × 1 — Use OEM specification
• O-ring seal (if not included with sensor) × 1 — Use OEM specification

Fluids

• Motorcraft Orange Coolant — 1 qt

Preparation

1. Ensure engine is completely cold to the touch
2. Park vehicle on level surface and engage parking brake
3. Open hood and locate coolant temperature sensor on driver side of engine block
4. Place drain pan beneath sensor location to catch coolant spillage

Procedure

1. 1

   Disconnect battery negative terminal
   Disconnect the negative battery cable to prevent electrical shorts and clear any stored fault codes. Use a 10mm wrench to loosen the terminal clamp and move cable away from battery post.
2. 2

   Access the coolant temperature sensor
   Locate the coolant temperature sensor on the driver side of the engine block, near the rear of the cylinder head below the intake manifold. You may need to remove the engine cover by pulling upward on the front tabs to improve access.
3. 3

   Disconnect sensor electrical connector
   Press the locking tab on the electrical connector and pull straight away from the sensor. Inspect connector terminals for corrosion or damage. Clean if necessary before reinstallation.
   ⚠Do not pull on wires; grasp only the connector body to prevent wire damage.
4. 4

   Drain coolant from sensor area
   Position drain pan directly below the sensor. Some coolant will drain when the sensor is removed. You can minimize spillage by removing the radiator cap slowly to relieve any residual pressure, then replacing it loosely to reduce coolant flow.
   ℹ️Approximately 0.5-1 quart of coolant will drain during sensor removal.
5. 5

   Remove old coolant temperature sensor
   Using a 19mm deep socket and ratchet, turn the sensor counterclockwise to remove. The sensor threads directly into the engine block. Work quickly once threads are disengaged to minimize coolant loss. Remove the old O-ring seal from the sensor bore if it remains in the block.
6. 6

   Prepare new sensor for installation
   Inspect the new sensor and confirm it includes a new O-ring seal. Apply a light coat of fresh coolant to the O-ring to aid installation. Do not use thread sealant or anti-seize on the sensor threads as this can cause false temperature readings due to electrical interference.
   ⚠Never apply thread sealant or anti-seize to coolant temperature sensor threads. This will cause inaccurate readings.
7. 7

   Install new coolant temperature sensor
   Thread the new sensor into the block by hand until it seats. Tighten to 15-20 Nm (11-15 lb-ft) using the 19mm socket. Do not overtighten as this can damage the sensor or crack the housing. The sensor should be snug but not excessively tight.
   ⚠Overtightening can crack the sensor housing or damage engine block threads.
8. 8

   Reconnect electrical connector
   Push the electrical connector onto the sensor until you hear and feel a positive click. Gently tug on the connector to verify it is fully locked. Apply dielectric grease to the connector seal if desired for additional moisture protection.
9. 9

   Refill cooling system
   Top off the cooling system with Motorcraft Orange Coolant to replace the coolant lost during sensor replacement. Fill through the degas bottle to the COLD FILL level. Do not overfill. Reinstall the radiator cap securely.
10. 10

    Reconnect battery and clear codes
    Reconnect the negative battery cable and tighten the terminal clamp. Start the engine and allow it to reach operating temperature while monitoring for coolant leaks around the new sensor. Check for proper temperature gauge operation on the instrument cluster.
11. 11

    Bleed cooling system and verify repair
    With engine at operating temperature, check coolant level in the degas bottle and top off if necessary. Allow engine to cool, then recheck level and add coolant to COLD FILL mark if needed. Use a scan tool to verify coolant temperature sensor is reading properly (should match actual engine temperature).
    ℹ️Temperature reading should gradually rise from ambient to approximately 195-220°F at operating temperature.

Reassembly

1. Reinstall engine cover if removed by aligning rear tabs first, then pressing down on front tabs until they click into place
2. Verify all tools and materials are removed from engine bay
3. Dispose of used coolant according to local environmental regulations

Verification

• Start engine and verify temperature gauge moves from cold to normal operating range within 5-10 minutes
• Check for coolant leaks around sensor with engine at operating temperature
• Use scan tool to confirm ECT sensor reads between 195-220°F when fully warmed up
• Verify no check engine light or temperature warning lights are illuminated
• Confirm cooling fans cycle on and off properly as temperature fluctuates

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