I have a 1993 Ford F-350 turbo-charged diesel quad-cab, 7.3 liter. I need to know how to change a serpentine belt--how does the idler-pulley work? Mine is loose and making contact with the fan blades.

REMOVAL & INSTALLATION-SERPENTINE (SINGLE) BELT
See Figure 21
http://www.autozone.com/images/cds/jpg/small/0900823d8009f298.jpg (javascript:pop()
Fig. 21: Pry back the serpentine belt tensioner and remove the belt from the pulleys

The serpentine belt drives the water pump, alternator, and (on some models) the air conditioner compressor.
http://www.autozone.com/images/upper_left.gifhttp://www.autozone.com/images/grey_line.gifhttp://www.autozone.com/images/upper_right.gif http://www.autozone.com/images/clearpixel.gifhttp://www.autozone.com/images/clearpixel.gif WARNING http://www.autozone.com/images/clearpixel.gif Check to make sure that the V-ribbed belt is located properly in all drive pulleys before applying tensioner pressure. http://www.autozone.com/images/clearpixel.gifhttp://www.autozone.com/images/clearpixel.gif http://www.autozone.com/images/lower_left.gifhttp://www.autozone.com/images/grey_line.gifhttp://www.autozone.com/images/lower_right.gif
Loosen the bracket lock bolt, retract the belt tensioner with a pry bar and slide the old belt off of the pulleys.
To install:
The spring powered tensioner automatically adjusts the belt to the proper tension.

Install the belt and release the tensioner. Tighten the lockbolt.


(this article was pasted here from Autozone)