there is a belt tensioner pulley that maybe is not working correctly
chainchain
timing BELT ( checked on 2007 )
Chain
You can do that by replacing the tensioner
depending on the style of belt, on the alternator belt there is an adjustment just below the slider holding the alternator, you just simply tighten it until belt becomes tight.
The belt has an automatic spring tensioner and can not be "tightened".
the belt is automatically tensioned by a spring loaded tensioner.
look in the instruction booklet
Tighten it or replace it.
The alternator will move in and out to tighten the belt and the PS pump will do the same
replace the spring loaded belt tensioner as it's the only thing that will keep the serpentine belt tight.
The fan is electric, not belt driven. The serpentine belt is has a spring loaded tensioner. If the belt is loose, the tensioner has failed.