How to Change '07 Mustang GT Thermostats

Ford started the "pony car" wars in 1964 when it released the legendary Mustang. The Mustang went through many growing pains throughout its life, none worse than the Mustang II era that ran from 1974 through 1978. The 2007 Mustang GT borrowed styling from the classic Mustangs of the 1960s and packed a 300-horsepower, 4.6-liter V-8 that would make its ancestors proud. A thermostat regulated the flow of coolant through this high-powered V-8 engine, helping to keep it within an acceptable temperature range. Replacing the thermostat in the 2007 Mustang GT is a job for an experienced do-it-yourself mechanic.

Instructions

Remove the negative battery cable from the battery, using a wrench, and position it aside.

Raise the front of the Mustang with a floor jack and slide jack stands under the subframe. Lower the vehicle until only the jack stands support its weight.

Slide a drain pan under the radiator petcock under the lower radiator hose and loosen the petcock by hand to start the coolant draining from the radiator. Once the flow of coolant stops, close the petcock by hand.

Raise the Mustang from the jack stands, using a floor jack, and pull the jack stands from under it. Lower the vehicle to the ground.

Pull the crankcase vent tube -- the small rubber tube -- from the air cleaner outlet tube -- the tube running from the air box to the engine. Loosen the clamps on either end of the air cleaner outlet hose, with a ratchet and socket, and pull it from the Mustang.

Confirm that the serpentine belt routing diagram on the radiator shroud is present and legible. If not, draw your own diagram. Set a ratchet and socket on the bolt in the center of the drive belt tensioner assembly pulley -- the arm and pulley assembly between the air-conditioner compressor and crankshaft pulley -- and turn the tensioner counterclockwise to release tension on the serpentine belt. Pull the serpentine belt from the vehicle. Inspect the belt for cracks or wear on the grooved side, and replace the belt if it has cracks.

Remove the power cable from the rear of the alternator, with a ratchet and socket. Unplug the wiring harness from the rear of the alternator.

Remove the two outer bolts on the alternator support bracket with a ratchet and socket. Remove the two lower alternator nuts, using a ratchet and socket, and pull the alternator from the engine. Locate the upper thermostat housing directly behind the alternator.

Remove the bolt on the driver's side of the upper thermostat with a ratchet and socket. Loosen the bolt on the passenger's side of the upper thermostat housing with a combination wrench. The passenger's side bolt only needs to be loosened as the housing has a slot where this bolt goes. Pull the upper thermostat housing from the lower thermostat housing, exposing the thermostat below it.

Pull the thermostat from the lower thermostat housing; take note of the old thermostat's position, as you must position the new thermostat in the same fashion. Insert the blade of a flat-head screwdriver under the O-ring in the lower thermostat housing and pry the O-ring out.

Coat the new O-ring in new coolant and insert it in the groove in the lower thermostat housing. Insert the new thermostat into the lower thermostat housing in the same position as the old thermostat.

Slide the upper thermostat housing on the lower thermostat housing, seating the bolt in the slot on the upper thermostat housing. Tighten the thermostat housing bolts to 8 foot-pounds. The driver's side bolt requires a torque wrench and socket to complete this task. The passenger's side bolt requires a torque wrench and box wrench ratchet attachment.

Set the alternator in place and hand-tighten its two bracket bolts and two nuts. Torque the two nuts to 18 foot-pounds and the two bracket bolts to 8 foot-pounds. Connect the power wire to the rear of the alternator and snug the nut with a ratchet and socket. Plug the wiring harness into the rear of the alternator.

Install the drive belt over all of the pulleys, starting with the alternator and working clockwise -- skip the tensioner pulley at this time.

Grab the drive belt where the tensioner pulley goes and hold it tight. Rotate the tensioner pulley clockwise to make clearance for the belt, using a ratchet and socket, and line the belt up with the tensioner pulley. Slowly guide the drive belt onto the tensioner pulley and remove the ratchet and socket from the tensioner pulley.

Reinstall the air cleaner output pipe onto the air box and throttle body. Tighten the hose clamps to 2 to 3 foot-pounds with a torque wrench and socket.

Set the negative battery cable back on the battery and tighten it to 3 to 4 foot-pounds with a torque wrench and socket.

Fill the radiator by adding 50-50 premixed Motorcraft Premium Gold Engine Coolant (or equivalent) into the degas bottle -- radiator overflow -- until the level is between the "Min" and "Max" marks on the bottle.

Turn the heater to its highest temperature setting and highest blower speed. Turn the air direction selector to blow air out of the vents on the face of the dashboard.

Start the Mustang's engine and allow it to idle until it reaches operating temperature -- about halfway on the temperature gauge.

Touch the upper radiator hose and check that it is hot to the touch. If it is, shut the engine down and allow it to cool. If not, allow the engine to run with constant temperature monitoring until the hose is hot. If the Mustang overheats, double check the installation of the thermostat.

Check the coolant level in the degas bottle and add 50-50 premixed Motorcraft Premium Gold Engine Coolant (or equivalent) until the level is between the "Min" and "Max" lines.