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

How do you change a tensioner pulley?
Flip the adjustment bolt privately, top or bottom of the pulley counterclockwise with the ratchet and socket before equipment belt is loose enough to remove. Tighten the tensioner pulley by turning the adjustment bolt clockwise with the ratchet and socket before 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 could cause power loss and harm to your belt-driven devices. You may have a failing tensioner pulley if you hear any squeaking or squealing beneath the hood. Bearings on the pulley can wear out, causing noise and high temperature. Pulleys are usually made of either plastic or steel, so verify the pulley itself for any damage aswell. At O’Reilly Auto Parts, we’ve tensioner pulleys available for many vehicle models.

The automatic pulley tensioner comes with an internal spring-loaded mechanism that keeps the serpentine belt under constant tension. Its design enables it to keep the serpentine belt taut, to ensure that the other item pulleys rotate at the same rpm (revolutions each and every minute) while under the same secure pressure. Tensioner pulleys can also absorb slight shock loads that happen when the air conditioner cuts on / off. As a continuously rotating element, the pulley tensioner can give off some indicators before failure.

Rust and Corrosion
The pulley tensioner sits subjected to the elements at the front end of the engine. Put through puddled water “splash-up,” with time the tensioner arm and pulley system can rust. Rust can freeze the automated tensioner device or corrode the shaft bearings, that will cause a frozen position in the adjustment pressure. Without the proper stress, the belt can slide.
Debris Contamination
Rocks, gravel and other highway debris can be thrown up into the tensioner pulley grooves and jam the system. This can allow the serpentine belt to slide on the tensioner pulley and burn. Overheated pulley heat range 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 strain on the pulley. Symptoms of a poor spring show as glazing on the underside of the serpentine belt, with an intermittent flickering of the dashboard’s charging lumination indicator. Squealing or squeaking will become read at the belt site.
Pulley Wobble
If the tensioner pulley wobbles on its shaft, it means the inside shaft bearings have worn. This will cause a pulley misalignment. Terrible bearings cause an audible growling sound. The outer ends of the serpentine belt will fray and extend the belt. Ultimately the rubberized belt grooves flatten out and cause key slippage. An excessively wobbling pulley can throw the belt off, creating all the gadgets to quit functioning.
Lever Arm Freeplay
Some tensioner pulleys possess markings on the casing that indicate the maximum 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 one position.
Pulley Misaligment
The tensioner pulley face must match up to the other accessory pulleys with a parallel alignment. Placing an extended, straightedge ruler against the facial skin of the tensioner pulley, and then flushing it against another item pulley, can measure the angle. Any off-angle measurement indicates donned shaft bearings in the pulley housing.
Serpentine Belt Noise
A moderately put on serpentine belt gives off a constant squeaking sound during engine idle. Belts which have worn severely project a loud chirping or squealing sound. The cause details to a glazed, donned or cracked belt. Dry or partially frozen tensioner pulley bearings can cause such sounds by wearing out the belt prematurely.
Lever Arm Oscillation
A lever arm that repeatedly oscillates back and forth during idle or higher speeds means the the within damper mechanism in the tensioner pulley has weakened or broken. This causes sporadic tension strain on the belt and can manifest itself with intermittent chirping sounds.