It is the Buick Drive Belt Tensioner and Pulley that keeps your serpentine belt snug against the accessories in the system they provide power too. The drive belt tensioner and pulley is the only roller on the front of the Buick engine that does not drive a component like the water pump or alternator.
The mechanical means that provides the force for the drive belt tensioner and pulley so friction can be applied to the serpentine belt is a spring in its inner workings. It is this spring?s tension that moves the pulley so it can automatically provide the tension against the drive belt system that must be maintained. Once this spring loses its ability to provide this tension, it has to be replaced.
The amount of force the Buick drive belt tensioner and pulley has can be tested by placing a socket and breaker bar on the center nut of this component. By removing the tension the drive belt tensioner and pulley is forcing against the serpentine belt, the actual amount of force in the spring can be felt. If only a little force is required to pull the pulley away and loosen the belt, the spring is losing its ability to perform its duty.
The Buick owner can also visually inspect this drive belt component by observing it when the engine is running. If the drive belt tensioner and pulley is moving excessively in which the tension on the serpentine belt varies as it rotates, the spring once again is worn past its expected lifespan.
If either of these inspections shows any evidence of the drive belt component failing, it should be replaced. This way the accessories on the front of your Buick engine will be provided with enough tension from the drive belt to supply the power to it so it can rotate without the belt slipping.