Coolant Temperature Sensor

This procedure covers the removal and replacement of the coolant temperature sensor on a 1972 Ford F-100 with a 302ci V8 engine.

Warnings

Tools required

Parts

• Coolant temperature sensor × 1 — Use OEM specification

Fluids

• Ethylene glycol green 50/50 — 1 qt

Preparation

1. Ensure the engine is completely cool to the touch
2. Park vehicle on level ground and engage parking brake
3. Place drain pan under the work area to catch coolant
4. Have replacement coolant available for topping off after repair

Procedure

1. 1

   Locate the coolant temperature sensor
   On the 302ci V8, the coolant temperature sending unit is threaded into the intake manifold at the front, near the thermostat housing. It has a single wire terminal connector. Note that on this pre-computer carbureted engine, this single unit typically drives the dash temperature gauge; verify the exact location against your specific intake manifold before proceeding. It has a single wire terminal connector. Do not confuse this with the temperature sending unit for the gauge, which may be located nearby. Verified detail (On the 1972 Ford 302, the coolant temperature sensor (sending unit) is typically located in the front of the intake manifold near the thermostat housing, but it's usually more center-front or slightly passenger side, not specifically driver's side. Location varies by intake manifold casting.): On the 302ci V8, the coolant temperature sensor is typically threaded into the front of the intake manifold, near the thermostat housing. Location may vary slightly depending on intake manifold casting.
2. 2

   Disconnect the electrical connector
   Pull the wire terminal connector straight off the coolant temperature sensor. Some resistance is normal; wiggle gently while pulling if needed. Inspect the connector terminal for corrosion or damage.
3. 3

   Drain coolant to below sensor level
   Open the radiator petcock or remove the lower radiator hose to drain coolant until the level drops below the sensor location. You do not need to drain the entire system, just enough to prevent excessive spillage when the sensor is removed. Typically 2-3 quarts will drain.
4. 4

   Remove the old coolant temperature sensor
   Using a deep socket or box-end wrench (typically 3/4" or 13/16" depending on sensor design), unscrew the coolant temperature sensor counterclockwise. Be prepared for residual coolant to drain from the opening. If the sensor is seized, apply penetrating oil and allow it to soak for 10-15 minutes before attempting removal again.
5. 5

   Clean the sensor port threads
   Use a wire brush and clean shop rags to remove old thread sealant, corrosion, and debris from the threads in the intake manifold. Ensure the sealing surface is clean and free of damage. Inspect threads for stripping or damage.
6. 6

   Prepare the new sensor
   Apply a thin coat of thread sealant with Teflon to the threads of the new coolant temperature sensor. Do not use pipe dope or tape that could contaminate the cooling system or interfere with the sensor's electrical ground path. Apply sealant only to the threads, keeping it away from the sensor tip.
7. 7

   Install the new sensor
   Thread the new coolant temperature sensor into the intake manifold by hand until it seats, then tighten with a wrench. Tighten firmly but do not overtighten; brass sensors can crack and aluminum threads can strip. Typical final tightness is 15.0 lb-ft (20.0 Nm).
8. 8

   Refill the cooling system
   Close the radiator petcock or reinstall the lower radiator hose if removed. Refill the cooling system with ethylene glycol green 50/50 coolant mixture to the proper level. The system capacity is approximately 14 quarts total (verify against your vehicle's specification); add approximately the amount drained plus additional to account for spillage. Verified detail (The 1972 Ford F-100 with 302ci V8 cooling system capacity is typically 14 quarts, not 15 quarts. This varies slightly by radiator type but 15 quarts appears high for this application.): The system capacity is approximately 14 quarts total
9. 9

   Reconnect the electrical connector
   Push the wire terminal connector firmly onto the new coolant temperature sensor until it seats completely. Ensure the connection is secure.
10. 10

    Bleed air from the cooling system
    With the radiator cap off, start the engine and allow it to idle until the thermostat opens and coolant begins to circulate. Add coolant as needed to maintain proper level. Watch for air bubbles and allow them to escape. Once the engine reaches normal operating temperature and no more air bubbles appear, shut off the engine and top off coolant to the full mark.

Reassembly

1. Reinstall the radiator cap securely
2. Wipe up any spilled coolant from engine surfaces and underneath the vehicle
3. Double-check that the sensor electrical connector is firmly attached

Verification

• Start the engine and allow it to reach normal operating temperature while monitoring for coolant leaks around the sensor
• Verify that the temperature gauge on the instrument cluster functions correctly and shows normal operating temperature
• Check coolant level after the engine has cooled and top off if necessary
• Inspect the sensor area for any signs of coolant seepage after the first drive cycle

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