The thermostat housing assembly on pickup trucks comes in different mounting configurations. Changing the unit may require removing two mounting bolts and some other engine accessories to reach the thermostat. Whichever your truck model, follow these steps to replace the thermostat in your truck.
Park your truck in a safe place and open the hood. Make sure the engine is cool enough to the touch. If it is at operating temperature, wait a few minutes for the engine to cool down.
Locate the thermostat housing on your engine. The best way is to follow the radiator upper hose towards the engine, then place a drain pan under the truck in the direction of the thermostat housing.
Remove the air duct or cleaner assembly to gain access to the thermostat housing if necessary. On some models, it is necessary to remove a steering pump-mounting bracket off the thermostat housing as well. Use a wrench or ratchet and socket to remove the bolts and bracket.
Unplug the sensor electrical connector from the thermostat housing if your model is equipped with one. Then remove the upper radiator hose from the thermostat housing by removing the clamp; use a Phillips screwdriver or ratchet and socket to loosen the clamp. Carefully twist and pull the hose off the housing and let the coolant drain onto the drain pan.
Remove the two thermostat housing mounting bolts using a wrench or ratchet and socket, then lift the housing off the engine and remove the thermostat and paper gasket or O-ring seal. Clean the housing and engine mounting surfaces of paper gasket material, using a plastic scraper if necessary.
Set the new thermostat in place with the spring pointing towards the engine. Install a new paper gasket or O-ring; apply a light coat of sealer to the gasket as recommended by the gasket manufacturer. Set the housing in place and start the mounting bolts by hand and then tighten the bolts.
Install the radiator upper hose and clamp over the thermostat housing. Also, install the power steering bracket and air cleaner assembly and plug the sensor electrical connector if you removed or disconnected them.
Start the engine and add 50 percent water and 50 percent antifreeze to the coolant reservoir. Let the engine reach operating temperature. Check for leaks and add coolant to the reservoir to bring the mixture level between the Add and Full Hot marks. Turn off the engine.
