The tensioner pulley on your Ford Explorer is on the front left side of the engine, typically on the lower end. The tensioner consists of a bracket or arm that bolts to the engine block and contains a spring in the mount to allow it to apply pressure to the belt. The second part is the pulley itself, which is mounted on the outer edge of the bracket or arm. If either portion of this assembly fails, it is often easier to replace it as one unit rather than try to get the pulley off the tensioner arm.
Remove the serpentine belt from the front of the engine. You must loosen the tension on it before it will come loose. There is a square hole in the tensioner arm where you can insert a breaker bar or large ratchet and move the arm to remove the tension.
Remove the four bolts holding the fan shroud to the radiator support. This will allow you to move it around, giving you more access to the tensioner and mounting bolt.
Locate the bolt in the center of the tensioner. There is one in the center of the pulley as well, but that will only remove the pulley and not the assembly.
Remove the mounting bolt in the center of the tensioner with a socket and ratchet. Be careful as you remove it, as it is spring-loaded.
Clamp the tensioner assembly in a vise so that it is secure. Use a socket and impact gun, if you have access to one, to remove the bolt in the center of the pulley. Remember to loosen this bolt in a clockwise direction; the threads are reversed on it.
Pull the pulley off the arm.
