What does the strain pulley do?
A drive belt tensioner is a pulley mounted on a spring mechanism or adjustable pivot point that is employed to keep tension on the engine belts. … Both are used to keeptension on the engine serpentine belts to ensure that they can drive the various engine accessories.

How do you adapt a tensioner pulley?
Flip the adjustment bolt on the side, top or bottom level of the pulley counterclockwise with the ratchet and socket before accessory belt is loose enough to eliminate. Tighten the tensioner pulley by turning the adjustment bolt clockwise with the ratchet and socket until the belt is tight.
How do you know

A tensioner pulley guides the belt around the tensioner and allows the belt to spin while the tensioner maintains pressure against it. A failing tensioner pulley can cause power loss and harm to your belt-driven systems. You may have a failing tensioner pulley if you hear any squeaking or squealing under the hood. Bearings on the pulley can degrade, causing noise and high temperature. Pulleys are usually manufactured from either plastic or steel, so check the pulley itself for any damage aswell. At O’Reilly Vehicle Parts, we’ve tensioner pulleys available for many vehicle models.

The computerized pulley tensioner has an internal spring-loaded mechanism that keeps the serpentine belt under regular tension. Its design enables it to keep the serpentine belt taut, in order that the other accessory pulleys rotate at the same rpm (revolutions each and every minute) while under the same safe pressure. Tensioner pulleys can also absorb moderate shock loads that happen when the air conditioning unit cuts on and off. As a frequently rotating component, the pulley tensioner can provide off some warning signs before failure.

Rust and Corrosion
The pulley tensioner sits subjected to the elements at the front of the engine. Subjected to puddled water “splash-up,” with time the tensioner arm and pulley mechanism can rust. Corrosion can freeze the automatic tensioner device or rot the shaft bearings, that may cause a frozen location in the adjustment pressure. Without the proper pressure, the belt can slip.
Debris Contamination
Rocks, gravel and other road debris could be thrown up in to the tensioner pulley grooves and jam the system. This can allow the serpentine belt to slip on the tensioner pulley and shed. Overheated pulley temp results, and finally the serpentine belt will melt and snap off.
Pulley Tensioner Spring
The pulley tensioner spring inside the housing can become weak from age and repeated contact with heat. This causes the belt to flutter and skip instead of maintaining a constant pressure on the pulley. Symptoms of a poor spring display as glazing on the underside of the serpentine belt, with an occasional flickering of the dashboard’s charging mild indicator. Squealing or squeaking will end up being listened to at the belt area.
Pulley Wobble
If the tensioner pulley wobbles on its shaft, this means the inside shaft bearings have worn. This may cause a pulley misalignment. Bad bearings cause an audible growling sound. The external ends of the serpentine belt will fray and stretch out the belt. Eventually the rubber belt grooves flatten out and cause key slippage. An excessively wobbling pulley can throw the belt off, leading to all the gadgets to quit functioning.
Lever Arm Freeplay
Some tensioner pulleys have markings on the housing that indicate the utmost range that the pulley can travel. If the lever arm of the tensioner rides under or higher the designated mark, this implies a stretched belt or a lever arm which has jammed in a single position.
Pulley Misaligment
The tensioner pulley face must match up to the other accessory pulleys with a parallel alignment. Placing a long, straightedge ruler against the face of the tensioner pulley, and then flushing it against another accessory pulley, can gauge the angle. Any off-position measurement indicates put on shaft bearings in the pulley casing.
Serpentine Belt Noise
A moderately put on serpentine belt gives off a constant squeaking noise during engine idle. Belts that have worn severely job a loud chirping or squealing audio. The cause items to a glazed, donned or cracked belt. Dry or partially frozen tensioner pulley bearings could cause such sounds by wearing out the belt prematurely.
Lever Arm Oscillation
A lever arm that repeatedly oscillates back and forth during idle or more speeds means the the inside damper mechanism in the tensioner pulley has weakened or broken. This causes sporadic tension strain on the belt and will manifest itself with intermittent chirping noises.