If your tensioner is "automatic", or spring loaded in other words. It is not adjustable in most cases. They are either good or bad. If the spring does not hold the belt tight any longer, the tensioner has to be replaced, no adjustments are able to be made.
The easiest way to loosen the tensioner is to use an automatic belt tensioner. This can be used on a serpentine belt which is connected to every pulley on the engine.belt.
Belt Tensioner All engines use an automatic drive belt tensioner. On the 7.5L engine, there are two belts; one uses the automatic tensioner, while the alternator belt requires periodic tensioning. On all belts using an automatic tensioner, no adjustment is necessary because the tensioner adjusts for belt wear. To adjust the tension on the 7,5L engine alternator belt, loosen the adjusting bolts and rotate the alternator until the proper tension is on the drive belt and tighten the adjusting bolts. It is recommended that the belt tension indicator mark be inspected with the engine OFF at 60,000 mile (96,000 km) intervals. If the wear indicator mark is out of specification, the drive belt is worn or an incorrect drive belt has been installed. The 4.6L, 5.4L, 6.8L, all have one belt and one belt tensioner. Look at the diagram on top of the radiator or somewhere in the engine compartment.
If you look carefully at the tensioner, you will see a square slot drive. Insert a ratchet in there and turn it. Can't remember if up or down, but you will see the tensioner slack enough to remove the belt.
Your Explorer has a serpentine belt tensioner which keeps the proper tension on the serpentine belt unless the tensioner has failed.
You can't adjust the chain on an LT80. You can buy an aftermarket chain tensioner if you wish to do this. This is the only way.
Belt Tensioner All engines use an automatic drive belt tensioner. On the 7.5L engine, there are two belts; one uses the automatic tensioner, while the alternator belt requires periodic tensioning. On all belts using an automatic tensioner, no adjustment is necessary because the tensioner adjusts for belt wear. To adjust the tension on the 7,5L engine alternator belt, loosen the adjusting bolts and rotate the alternator until the proper tension is on the drive belt and tighten the adjusting bolts. It is recommended that the belt tension indicator mark be inspected with the engine OFF at 60,000 mile (96,000 km) intervals. If the wear indicator mark is out of specification, the drive belt is worn or an incorrect drive belt has been installed. The 4.6L, 5.4L, 6.8L, all have one belt and one belt tensioner. Look at the diagram on top of the radiator or somewhere in the engine compartment. 1/2" ratchet / or 1/2" beaker bar will do the trick.
If the tensioner isn't tight enough it's probably the spring. You can purchase a serpentine belt tensioner to replace the one that has become weak.
Belt Tensioner All engines use an automatic drive belt tensioner. On the 7.5L engine, there are two belts; one uses the automatic tensioner, while the alternator belt requires periodic tensioning. On all belts using an automatic tensioner, no adjustment is necessary because the tensioner adjusts for belt wear. To adjust the tension on the 7,5L engine alternator belt, loosen the adjusting bolts and rotate the alternator until the proper tension is on the drive belt and tighten the adjusting bolts. It is recommended that the belt tension indicator mark be inspected with the engine OFF at 60,000 mile (96,000 km) intervals. If the wear indicator mark is out of specification, the drive belt is worn or an incorrect drive belt has been installed. The 4.6L, 5.4L, 6.8L, all have one belt and one belt tensioner. Look at the diagram on top of the radiator or somewhere in the engine compartment.
Check the Belt Tensioner All engines use an automatic drive belt tensioner. On the 7.5L engine, there are two belts; one uses the automatic tensioner, while the alternator belt requires periodic tensioning. On all belts using an automatic tensioner, no adjustment is necessary because the tensioner adjusts for belt wear. To adjust the tension on the 7,5L engine alternator belt, loosen the adjusting bolts and rotate the alternator until the proper tension is on the drive belt and tighten the adjusting bolts. It is recommended that the belt tension indicator mark be inspected with the engine OFF at 60,000 mile (96,000 km) intervals. If the wear indicator mark is out of specification, the drive belt is worn or an incorrect drive belt has been installed. The 4.6L, 5.4L, 6.8L, all have one belt and one belt tensioner. Look at the diagram on top of the radiator or somewhere in the engine compartment. Also, Check your alternator
There is no "fan belt"; the 2.5L V-6 has two accessory drive belts, both with tensioners (loosen the large nut in the center of the tensioner pulley, and adjust the threaded adjustment rod), and the 2.0L I-4 has a single accessory drive belt with a tensioner (loosen the clamp bolt & adjust the threaded adjustment rod).
I replaced an alternator on a 2002 Nissan Altima but the drive belt is now too loose even with it having an automatic belt tensioner
To change belt use a breaker bar and extension to relieve tension To change tensioner unbolt To change wheel (left hand thread)