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

How do you adjust a tensioner pulley?
Flip the adjustment bolt privately, top or bottom of the pulley counterclockwise with the ratchet and socket before accessory 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 tutorials 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 reduction and harm to your belt-driven systems. You might have a failing tensioner pulley if you hear any squeaking or squealing beneath the hood. Bearings on the pulley can degrade, causing noise and warmth. Pulleys are usually made of either plastic or metallic, so examine the pulley itself for just about any damage as well. At O'Reilly Auto Parts, we have tensioner pulleys designed for many vehicle models.

The automatic pulley tensioner has an internal spring-loaded mechanism that keeps the serpentine belt under continuous tension. Its design enables it to keep carefully the serpentine belt taut, to ensure that the other equipment pulleys rotate at the same rpm (revolutions per minute) while under the same secure pressure. Tensioner pulleys can also absorb moderate shock loads that happen when the air conditioner cuts on and off. As a continuously rotating part, 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," as time passes the tensioner arm and pulley device can rust. Corrosion can freeze the programmed tensioner device or rot the shaft bearings, that may cause a frozen job in the adjustment pressure. Without the proper stress, the belt can slip.
Debris Contamination
Rocks, gravel and other street debris can be thrown up in to the tensioner pulley grooves and jam the system. This can permit the serpentine belt to slide on the tensioner pulley and melt away. 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 triggers the belt to flutter and skip rather than maintaining a constant pressure on the pulley. Symptoms of a poor spring display as glazing on the lower of the serpentine belt, with an intermittent flickering of the dashboard's charging mild indicator. Squealing or squeaking will end up being heard at the belt location.
Pulley Wobble
If the tensioner pulley wobbles on its shaft, it means the inside shaft bearings have worn. This may cause a pulley misalignment. Awful bearings trigger an audible growling sound. The outer ends of the serpentine belt will fray and extend the belt. Sooner or later the rubberized belt grooves flatten out and cause significant slippage. An excessively wobbling pulley can toss the belt off, creating all the equipment to quit functioning.
Lever Arm Freeplay
Some tensioner pulleys have markings on the casing that indicate the maximum range that the pulley can travel. If the lever arm of the tensioner rides under or over the designated mark, this implies a stretched belt or a lever arm that has jammed in a single position.
Pulley Misaligment
The tensioner pulley face must match to the other accessory pulleys with a parallel alignment. Placing a long, straightedge ruler against the facial skin of the tensioner pulley, and flushing it against another item pulley, can measure the angle. Any off-angle measurement indicates put on shaft bearings in the pulley casing.
Serpentine Belt Noise
A moderately worn serpentine belt gives off a constant squeaking noises during engine idle. Belts that have worn severely job a loud chirping or squealing sound. The cause items to a glazed, donned or cracked belt. Dried out or partially frozen tensioner pulley bearings could cause such noises by deteriorating the belt prematurely.
Lever Arm Oscillation
A lever arm that repeatedly oscillates backwards and forwards during idle or higher speeds means the the within damper mechanism in the tensioner pulley has weakened or broken. This causes sporadic tension pressure on the belt and will manifest itself with intermittent chirping noises.