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

How do you change a tensioner pulley?
Transform the adjustment bolt privately, top or bottom of the pulley counterclockwise with the ratchet and socket until the 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 manuals 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 could 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 heating. Pulleys are usually manufactured from either plastic or steel, so verify the pulley itself for any damage aswell. At O’Reilly Car Parts, we’ve tensioner pulleys designed for many vehicle models.

The automatic pulley tensioner has an internal spring-loaded mechanism that keeps the serpentine belt under frequent tension. Its design allows it to keep the serpentine belt taut, in order that the other accessory pulleys rotate at the same rpm (revolutions per minute) while under the same safe pressure. Tensioner pulleys may also absorb slight shock loads that happen when the air conditioning unit cuts on / 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 end of the engine. Subjected to puddled water “splash-up,” with time the tensioner arm and pulley mechanism can rust. Corrosion can freeze the automated tensioner device or corrode the shaft bearings, that may cause a frozen position in the adjustment pressure. Without the correct pressure, the belt can slide.
Debris Contamination
Rocks, gravel and other highway debris could be thrown up into the tensioner pulley grooves and jam the system. This can permit the serpentine belt to slide on the tensioner pulley and shed. Overheated pulley heat range results, and eventually the serpentine belt will melt and snap off.
Pulley Tensioner Spring
The pulley tensioner spring in the housing can become weak from age and repeated exposure to heat. This triggers the belt to flutter and skip rather than maintaining a constant strain on the pulley. Symptoms of a weak 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 be listened to at the belt location.
Pulley Wobble
If the tensioner pulley wobbles on its shaft, this means the inside shaft bearings have worn. This may cause a pulley misalignment. Poor bearings cause an audible growling sound. The outer ends of the serpentine belt will fray and stretch out the belt. Finally the rubberized belt grooves flatten out and trigger major slippage. An excessively wobbling pulley can throw the belt off, creating all the add-ons to quit functioning.
Lever Arm Freeplay
Some tensioner pulleys have markings on the casing that indicate the utmost range that the pulley can travel. If the lever arm of the tensioner rides under or over the designated mark, it indicates a stretched belt or a lever arm which has jammed in one position.
Pulley Misaligment
The tensioner pulley face must match to the other accessory pulleys with a parallel alignment. Placing an extended, straightedge ruler against the face of the tensioner pulley, and flushing it against another accessory pulley, can gauge the angle. Any off-angle measurement indicates put on 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 may have worn severely job a loud chirping or squealing audio. The cause tips to a glazed, donned or cracked belt. Dried out or partially frozen tensioner pulley bearings could cause such noises by wearing out the belt prematurely.
Lever Arm Oscillation
A lever arm that repeatedly oscillates backwards and forwards during idle or more speeds means the the within damper mechanism in the tensioner pulley has weakened or broken. This causes sporadic tension pressure on the belt and can manifest itself with intermittent chirping sounds.