2009-2010 Ford Mustang 4.6L
With Ford Mustang 2009-2010 4.6L Engine model, the serpentine belt tensioner will set its tension automatically on the belt, and there won’t be a separate adjustment required. You can check and verify if the correct belt is used and installed when you notice the tension is not properly set. Also check if the belt is mounted in right position.
As part of a routine check, make sure there are no signs of glazing or cracking around the belt when you inspect. If the belt became glazed, then it will be perfectly smooth from slippage, and if it’s good condition, then it will have a slight texture of fabric visible.
Also note that any crack will start to develop from inner edge of the belt and it becomes growing outward. Therefore you should replace a damaged serpentine belt immediately.
Removal and Install:
Use the tensioner release tool, as it is better than using by hands or screwdrivers. By rotating the drive belt tensioner clockwise, you should be able to remove the belt easily. When you install, follow the instruction in reverse order of removal procedure.