This procedure covers the replacement of the coolant temperature sensor (CHT or ECT sensor) on the 3.5L EcoBoost engine, including coolant partial drain, sensor removal, installation, and system refill.

Warnings

Tools required

Parts

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

Fluids

• Motorcraft Orange Coolant — 2 qt

Preparation

1. Ensure engine is completely cool to the touch
2. Park vehicle on level surface and engage parking brake
3. Disconnect negative battery cable to prevent fault codes during sensor disconnection
4. Locate the coolant temperature sensor on your specific engine (consult service manual diagram if unsure)
5. Place drain pan under radiator drain plug or petcock

Procedure

1. 1

   Partially drain cooling system
   Open the radiator drain plug or petcock and drain coolant until the level is below the sensor location. For most sensor positions on the 3.5L EcoBoost, draining approximately 2-3 quarts is sufficient. Close drain plug when complete.
   Torque spec

   Coolant Drain Plug15 Nm (11 lb-ft)

   Drain Petcock8 Nm (6 lb-ft)
2. 2

   Remove engine cover if equipped
   Remove the plastic engine cover by pulling upward on the cover to disengage the retaining grommets. Set aside in a clean area.
3. 3

   Access coolant temperature sensor
   Locate the coolant temperature sensor. On the 3.5L EcoBoost, this is typically located on the coolant crossover pipe or cylinder head. Remove any wiring harness clips or covers that obstruct access to the sensor.
4. 4

   Disconnect electrical connector
   Press the locking tab on the sensor electrical connector and carefully pull the connector straight off the sensor. Inspect the connector terminals for corrosion or damage.
5. 5

   Remove old sensor
   Using the appropriate socket (typically 19mm or 22mm deep socket), carefully unscrew the coolant temperature sensor. Expect residual coolant to drain from the opening. Have a shop towel ready to catch spillage.
   ⚠Do not use excessive force as the sensor housing can crack if overtightened previously. If sensor is seized, apply gentle heat to surrounding area.
6. 6

   Prepare new sensor
   Inspect the new sensor and verify it matches the old unit. Check that the O-ring or seal is properly seated in the sensor body. If the seal is separate, install it onto the new sensor. Do not apply thread sealant unless specifically called for by the sensor manufacturer.
7. 7

   Install new sensor
   Thread the new sensor into the mounting location by hand, ensuring it starts straight and threads smoothly. Once hand-tight, use a torque wrench to tighten to specification. Note: If no specific torque spec is provided with the sensor, tighten to 8-12 lb-ft (11-16 Nm) for typical brass sensors.
   ⚠Over-tightening can crack the sensor body or damage threads in the aluminum housing. Use a torque wrench.
8. 8

   Reconnect electrical connector
   Push the electrical connector onto the new sensor until it clicks into place. Verify the locking tab is fully engaged. Reinstall any wiring harness clips or covers.
9. 9

   Refill cooling system
   Using a funnel, add Motorcraft Orange Coolant to the degas bottle or radiator fill point until coolant reaches the COLD FILL level. If bleeder screw is accessible on the cooling system, open it slightly during fill until coolant flows without air bubbles, then close.
   Torque spec

   Bleed Screw8 Nm (6 lb-ft)
10. 10

    Bleed cooling system
    Start the engine and allow it to reach normal operating temperature with the heater on maximum. Monitor coolant level and add as necessary. Rev engine to 2000-2500 RPM several times to help purge air. Watch for leaks around the new sensor.
    ⚠Monitor temperature gauge closely. If engine begins to overheat, shut off immediately as air may still be trapped in the system.
11. 11

    Final coolant level check
    After engine cools completely, recheck coolant level in degas bottle and top off to COLD FILL mark if necessary. Check for any coolant leaks around sensor installation point.
12. 12

    Reinstall components and clear codes
    Reinstall engine cover by aligning grommets and pressing down firmly. Reconnect negative battery cable. Use a scan tool to clear any diagnostic trouble codes that were set during the repair.

Reassembly

1. Ensure all electrical connectors are fully locked in place with audible clicks
2. Verify no tools or shop towels were left in the engine bay
3. Inspect ground under vehicle for any coolant drips after test drive

Verification

• Use a scan tool to verify the coolant temperature sensor is reading correctly (should show ambient temperature when cold, rising smoothly to 180-220°F during warm-up)
• Confirm no diagnostic trouble codes related to coolant temperature (P0115, P0116, P0117, P0118)
• Verify engine reaches normal operating temperature and cooling fans cycle on/off properly
• Check temperature gauge on instrument cluster displays normal operating temperature
• Inspect sensor installation point for any coolant leaks after engine reaches operating temperature
• Test drive vehicle and verify no overheating occurs and temperature remains stable

More procedures for this vehicle