F 150 Heritage 4WD Pickup V6-4.2L VIN 2 (2004)
4.6L, 5.4L Belt, Drive Tensioner/Belt Length Indicator Without A/C
Automatic tensioners are calibrated at the factory to idle the correct amount of tension to the belt. Unless a spring within the tensioner assembly breaks
or some other mechanical part of the tensioner falls, there is no need to check tensioners for proper tension.
The only mechanical check that need be made, if you have any doubt about the tensioner function, would be to remove the belt in the area of the
tensioner, to avoid belt contact, then using the proper tool, rotate the tensioner from its relaxed position through its full stroke and back to the relaxed
position to assure that there is no "stick, grab, bind," and to assure that there is tension on the spring. It is a normal condition for the tensioner to be
moving, under certain conditions, when the engine is running. If the tensioner meets these criteria, it should be assumed to be a good tensioner.
