You can't, the serpentine belt (or fan belt) on a grand marquis is equiped with a self tensioner, if your belt is making noise it either needs to be replaced or one of the pulleys on the cars may be loose and would need to be replaced.
routing for serpentine belt 2003 mercury sable
diagram for 2003 grand marquis belt installation
You cannot adjust the tension on this, it has a spring inside of it. If it is weak, it must be replaced.
NO belt in the 302cid engine of a 1988 Mercury Grand Marquis. it is a chain with gears
you do not adjust tension on a serpentine belt the tension is automatcally adjusted if the belt is loose, replace the belt SOME TIMES THE TENSIONER CAN BE WEEK ALSO.
Sometimes it has to be removed, sometimes you can loosen it on one side to be able to slip the belt past to remove and replace it.
Done automatically by belt tensioner
Your Explorer has a serpentine belt tensioner which keeps the proper tension on the serpentine belt unless the tensioner has failed.
In the belt book at most autoparts stores have a diagram section for serpentine belt routing.
when the belt has no slack in it
u do not adjust belt tensioner if belt is loose, u need to replace belt as tensioner works automatically
You have to release your tensioners in order to release your serpentine belt. When you put the belt back on you have to follow the diagram on the hood of your car.