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

How do you adjust a tensioner pulley?
Turn the adjustment bolt on the side, top or bottom of the pulley counterclockwise with the ratchet and socket until the 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 tutorials the belt around the tensioner and allows the belt to spin as the tensioner maintains pressure against it. A failing tensioner pulley can cause power loss and harm to your belt-driven devices. You could have a failing tensioner pulley if you hear any squeaking or squealing beneath the hood. Bearings on the pulley can degrade, causing noise and heating. Pulleys are usually made of either plastic or metallic, so verify the pulley itself for any damage aswell. At O’Reilly Automobile Parts, we have tensioner pulleys available for many vehicle models.

The automated pulley tensioner has an internal spring-loaded mechanism that keeps the serpentine belt under constant 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 can also absorb moderate shock loads that happen when the air conditioner cuts on and off. As a frequently 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 end of the engine. Subjected to puddled water “splash-up,” as time passes the tensioner arm and pulley device can rust. Rust can freeze the automated tensioner device or corrode the shaft bearings, that will cause a frozen location in the adjustment pressure. Without the correct tension, the belt can slip.
Debris Contamination
Rocks, gravel and other road debris can be thrown up into the tensioner pulley grooves and jam the mechanism. This can permit the serpentine belt to slip on the tensioner pulley and burn up. Overheated pulley heat results, and finally 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 instead of maintaining a constant strain on the pulley. Symptoms of a weak spring display as glazing on the lower of the serpentine belt, with an intermittent flickering of the dashboard’s charging light indicator. Squealing or squeaking will be observed at the belt area.
Pulley Wobble
If the tensioner pulley wobbles on its shaft, this means the interior shaft bearings have worn. This may cause a pulley misalignment. Undesirable bearings cause an audible growling noise. The external ends of the serpentine belt will fray and extend the belt. Gradually the rubberized belt grooves flatten out and trigger important slippage. An excessively wobbling pulley can toss the belt off, leading to all the equipment 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 one 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 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 worn serpentine belt produces a constant squeaking noises during engine idle. Belts which may have worn severely project a loud chirping or squealing appear. The cause factors to a glazed, worn or cracked belt. Dried out 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 backwards and forwards during idle or higher speeds means the the within damper mechanism in the tensioner pulley has weakened or broken. This triggers sporadic tension strain on the belt and will manifest itself with intermittent chirping sounds.