How to Change the Thermostat on a 1987 Ford F150

When replacing coolant hoses on a 1997 Ford F150, or doing any other cooling system work, it's always a good idea to replace the thermostat as well. Thermostats are made from inexpensive materials and are easy to replace--and doing so is good preventive maintenance. If the thermostat should stick open, the F150 will run poorly, as it will be unable to achieve full operating temperature. If the thermostat sticks closed, the F150 will run fine until it overheats and leaves you stranded. For anyone with basic mechanical skills and a few tools, this job won't take more than 30 minutes.

Tools Used: Catch pan, Socket set, Pocket screwdriver, Replacement thermostat housing (optional), Gasket scraper, Rags, Replacement thermostat, Black RTV, Coolant

Change the Thermostat

Raise the hood, locate the upper radiator hose and place the catch pan on the ground directly below the hose.

Release the hose clamp located at the engine side of the upper radiator hose with the socket set. Pull the hose off the thermostat housing by hand, and aim it down at the catch pan so any coolant in the hose will pour into the catch pan and not create a mess. You may need to coax the hose loose by inserting the pocket screwdriver between it and the thermostat housing if the hose hasn't been removed in a long time.

Remove the bolts holding the thermostat housing to the top of the intake manifold with the socket set. Pull the housing off by hand once the bolts are out. If the housing doesn't come off easily, you can insert the head of the socket wrench into the housing inlet and use it to lever the housing loose. Once off, examine it carefully for signs of pitting or corrosion, and replace it if you notice any. This is common in high-mileage engines. If the housing is not being replaced, scrape any leftover adhesive away from it and the intake manifold's sealing surfaces.

Pull the old thermostat out by hand and wipe the area clean with a rag. Note how the thermostat was sitting in the intake manifold, including the orientation. Insert the replacement thermostat into the manifold in the same position and orientation as the old one. Make sure the O-ring is properly seated on the thermostat's flange before putting the thermostat into the manifold.

Wipe a thin layer of black RTV adhesive onto the thermostat housing sealing surface and put the housing in position. Thread the bolts back into place by hand and tighten them down with the socket set.

Push the radiator hose onto the thermostat housing inlet and tighten the hose clamp back down. Top the coolant level if you lost any during Step 2.

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