The thermostat in a 1997 Ford Explorer regulates the coolant flow in order to keep the engine operating at the designed temperature. When you start the Explorer, the thermostat remains closed, preventing coolant from removing heat from the engine block. It opens when the engine hits the desired temperature to draw heat away and keep the engine from overheating. You should replace the thermostat every time you perform any cooling system work. Anyone with basic auto-repair skill can do just that in less than an hour.
Open the Explorer's hood and slide the catch pan under the engine until it sits directly below the thermostat housing. You can locate the housing by following the upper radiator hose from the radiator to the engine. The hose connects to the thermostat housing.
Loosen the hose clamp on the upper radiator hose where it joins the thermostat housing, using the socket set. Slide the clamp back along the hose by hand.
Remove the hose from the thermostat housing by hand and aim the open end down at the catch pan so that any coolant in the hose flows into the pan.
Remove the bolts holding the thermostat housing in place, using the socket set. Pull the housing off the intake manifold by hand. If it won't come off easily; insert the handle of your socket wrench into the hose inlet on the housing and use the wrench to lever the housing loose.
Remove the thermostat and old O-ring by hand after noting their positions and orientation. Set the new thermostat and O-ring into the manifold in their place. If the O-ring wasn't on the thermostat in the packaging, simply put it around the thermostat's center flange by hand before inserting the thermostat into the manifold.
Set the Explorer's thermostat housing back into place on the manifold and thread the bolts in by hand. Tighten the bolts with the socket set.
Slide the upper radiator hose over the thermostat housing hose inlet. Slide the hose clamp back into position and tighten it with the socket set.
Add an equal amount of Ford Coolant and distilled water to the coolant overflow bottle to offset the amount of coolant you lost when removing the upper radiator hose in Step 3.
