What does the tension pulley do?
A drive belt tensioner is a pulley mounted on a spring mechanism 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 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 courses 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 damage to your belt-driven systems. You might have a failing tensioner pulley if you hear any squeaking or squealing under the hood. Bearings on the pulley can degrade, causing noise and heating. 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 automatic pulley tensioner comes with an internal spring-loaded mechanism that keeps the serpentine belt under frequent tension. Its design allows it to keep carefully the serpentine belt taut, so that the other equipment 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 conditioner cuts on and off. As a constantly rotating element, the pulley tensioner can provide off some warning signs before failure.

Rust and Corrosion
The pulley tensioner sits exposed to the elements at the front of the engine. Subjected to puddled water “splash-up,” as time passes the tensioner arm and pulley system can rust. Corrosion can freeze the automatic tensioner device or rot the shaft bearings, that will cause a frozen placement in the adjustment pressure. Without the proper stress, the belt can slip.
Debris Contamination
Rocks, gravel and other street debris could be thrown up in to the tensioner pulley grooves and jam the mechanism. This can permit the serpentine belt to slip on the tensioner pulley and burn. Overheated pulley temp results, and finally the serpentine belt will melt and snap off.
Pulley Tensioner Spring
The pulley tensioner spring inside housing can become weak from age and repeated exposure to heat. This causes the belt to flutter and skip instead of maintaining a constant pressure on the pulley. Symptoms of a fragile spring display as glazing on the lower of the serpentine belt, with an occasional flickering of the dashboard’s charging lumination indicator. Squealing or squeaking will end up being heard at the belt position.
Pulley Wobble
If the tensioner pulley wobbles on its shaft, it means the inside shaft bearings have worn. This may cause a pulley misalignment. Bad bearings cause an audible growling sound. The outer ends of the serpentine belt will fray and stretch out the belt. Finally the rubber belt grooves flatten out and cause important slippage. An excessively wobbling pulley can toss the belt off, creating all the extras to quit functioning.
Lever Arm Freeplay
Some tensioner pulleys have markings on the housing that indicate the maximum selection 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 facial skin of the tensioner pulley, and then flushing it against another item pulley, can gauge the angle. Any off-position measurement indicates donned shaft bearings in the pulley casing.
Serpentine Belt Noise
A moderately donned serpentine belt gives off a constant squeaking sound during engine idle. Belts which have worn severely job a loud chirping or squealing audio. The cause things to a glazed, worn or cracked belt. Dried out or partially frozen tensioner pulley bearings could cause such sounds by deteriorating the belt prematurely.
Lever Arm Oscillation
A lever arm that repeatedly oscillates backwards and forwards 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.