How Replace the Thermostat in a 2001 F150

by Kyle McBride

    The 2001 Ford F-150 series trucks with the 4.6-liter or 5.4-liter V-8 engines are equipped with a 19.4-quart liquid cooling system. Coolant made up of water and antifreeze is circulated through the water jackets to draw waste heat away from the truck's engine. The thermostat remains closed while the coolant is below 188 degrees F to help the engine warm up. Once the engine coolant warms up to between 188 and 195 degrees F, the thermostat starts to open to allow the coolant to circulate through the radiator until the thermostat is fully open at 208 to 215 degrees F. Thermostats can fail over time, causing the engine to overheat, or over-cool.

    Items you will need

    • Thick, clean rag
    • Drain pan
    • Open-end wrench set
    • Pliers
    • Shop rag
    • Ratchet
    • Ratchet extension
    • Socket set
    • New thermostat and O-ring
    • Foot-pound torque wrench
    • Ford Premium Engine Coolant E2FZ-19549-AA (F5FZ-19459-AA in Oregon) or equivalent meeting Ford specifications ESE-M97B44-A

    Depressurizing and Draining the Cooling System

    Step 1

    Allow the engine to cool completely. Wrap a thick, clean rag around the degas bottle pressure cap. Slowly rotate the degas pressure cap counterclockwise until the residual pressure within the system begins to leak. Step away from the vehicle until the hissing sound of the pressure escaping dissipates. Remove the degas bottle pressure cap.

    Step 2

    Find the radiator draincock at the bottom, passenger-side corner of the radiator. Place a drain pan under the draincock.

    Step 3

    Open the radiator draincock using an open-end wrench. Drain approximately 1/2 gallon of coolant from the radiator. Close the radiator draincock. Set the drained coolant aside.

    Removing and Replacing the Thermostat

    Step 1

    Find the thermostat housing on the front of the engine where the top radiator hose connects to the engine. Open the radiator hose clamp using pliers and slide the clamp along the hose towards the radiator until the clamp clears the thermostat housing. Pull the hose off the housing.

    Step 2

    Wipe the thermostat housing and surrounding areas using a shop rag to remove dirt or debris that could fall into the thermostat hole once you remove the housing and thermostat.

    Step 3

    Remove the two thermostat housing retaining bolts using a ratchet, extension and socket. Lift the housing straight up and remove it from the intake manifold. Note the thermostat's position before you remove it from the engine block. Remove the O-ring seal and thermostat from the engine block. Discard the O-ring seal.

    Step 4

    Install the new thermostat in the same position in its recess in the intake manifold. Install a new O-ring seal on top of the thermostat.

    Step 5

    Install the thermostat housing and retaining bolts. Torque the retaining bolts to 20 foot-pounds, using a torque wrench, extension and socket.

    Step 6

    Install the radiator hose on the thermostat housing. Open the radiator hose clamp using a pliers and slide the clamp up the hose until the clamp is within about a 1/2 inch of the end of the hose. Release the pliers to seat the clamp.

    Filling the Cooling System

    Step 1

    Pour the drained coolant into the degas bottle. Add new coolant to the degas bottle until the fluid level is between the “Coolant Fill Level” marks, if the level is low.

    Step 2

    Set the cabin temperature blend control to the full warm position. Start the engine and allow it to reach operating temperature. Check the draincock, thermostat housing and radiator hose areas for leaks.

    Step 3

    Add engine coolant to the degas bottle until the fluid level is between the “Coolant Fill Level” marks. Turn the engine off and allow it to cool completely.

    Step 4

    Repeat steps 2 through 4 until the coolant level in the degas bottle stabilizes between the “Coolant Fill Level” marks.


    • In the 4.2-liter V-6 engine, the procedure is the same; however the thermostat is mounted horizontally into the front of the engine instead of vertically into the intake manifold. Torque the housing bolts to 80 inch-pounds.
    • If you plan to reuse the coolant drained from the radiator, use a clean drain pan. If the truck overheated, use fresh coolant. Do not use the drained coolant if it is discolored or shows signs of contamination. If discolored or contaminated, flush the cooling system and replace with fresh coolant.


    • Never open the cooling system while the engine is hot. Pressure within the system can forcefully discharge hot coolant and steam, and can cause personal injury.
    • Always use a 50/50 mix of approved coolant and clean water.
    • In the 2001 F-150, do not use orange-colored, extended-life coolant, mix coolant types or add methanol or alcohol to the coolant.
    • Do not use recycled coolant unless it meets Ford specification ESE-M97B44-A.
    • Discard any waste coolant in accordance with local ordinances. Do not discard coolant onto the ground or pour it down a sink or storm drain. Coolant is toxic, so clean up spills immediately.


    • 2001 F-150 Workshop Manual; Ford Motor Company; 2002

    Photo Credits

    • marla chebby/iStock/Getty Images