The serpentine belt debuted in the 1979 Ford Mustang together with the automatic belt tensioner assembly. While we have actually seen good enhancements in belt construction and longevity with EPDM rubber products, the design of the spring-loaded automatic belt tensioner has stayed mostly unadjusted.

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Most serpentine belt requests take place after the customer notices the squealing or chirping noises. These are generally linked via imappropriate belt anxiety and also misalignment. However, replacing the belt alone seldom resolves the worry. The best means to proccasion comebacks and also “defective” belt clintends is to replace the tensioner assembly and also associated pulleys, and also recommend a thostormy inspection of the other belt-propelled components.

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A worn or glazed serpentine belt may begin to squeal through age. Squealing from a freshly reput belt commonly suggests a larger problem: Imcorrect Tension. The automatic belt tensioner is designed to provide constant stress for the life of the belt. Heat and also recurring cycling of the tensioner’s internal spring can lead to exhaustion and also loss of tension. Loss of lubrication, and foreign contaminants inside the tensioner housing, may cause binding and also limit the full travel of the tensioner arm. These deserve to compromise the efficiency of the tensioner by offering too bit (or also much) stress. Overtensioned belts seldom squeal, yet have the right to reason various other worries. Squealing is mainly because of slippage, and also is the many noticeable symptom of low belt stress.

The belt tensioner not only offers the correct amount of tension, however likewise absorbs shocks and also vibrations from the rest of the drive system. A damper inside the tensioner housing reduces the activity of the tensioner arm, while taking in vibrations and reducing noise. Excessive oscillation of the tensioner arm is a symptom of damper failure and also spring tiredness. It additionally may be an indication of component faientice elsewhere in the accessory drive mechanism.


Serpentine belt misalignment can be led to by any kind of of the accessory pulleys. Or, it might be the outcome of improper belt installation. Tbelow are 2 kinds of misalignment, each resulted in by the relationship of the pulleys to one another.

Angular Misalignment

This occurs when pulleys become “tilted” because their shafts are not parallel. Worn bushings and also bearings deserve to permit rotating shafts to end up being cockeyed in their bores. Premature bearing and also bushing wear is regularly resulted in by the strain of too much belt stress. Installing a belt that is shorter than the original, or attempting to bypass a component like an A/C compressor, have the right to transform the amount of tension. This deserve to reduce belt life and accelerate wear on various other components. Likewise, substituting larger pulleys deserve to have actually the very same impact, and also decrease the output of alternators and power steering pumps. Angular misalignment can likewise originate from the tensioner itself as the interior pivot bushing wears and the tensioner arm begins to tilt. This likewise may cause binding between the housing and arm, which leads to anxiety issues.

Parallel Misalignment

When a wheel is “out of plane” via the other pulleys in the drive device, parallel misalignment occurs. While every one of the pulleys might be running true, one or even more of them could be sitting too far forward or earlier on its shaft. A prevalent source of parallel misalignment is imappropriate installation depth of press-fit pulleys, choose those uncovered on power steering pumps. The outer ring of a worn harmonic balancer may begin to “walk” from its hub, bring about a similar misalignment. In either kind of misalignment, the belt will certainly track at an angle, resulting in increased wear on the ribs and also belt edges. The added friction additionally boosts the operating temperature of the belt. This can substantially decrease belt performance and also service life. Misalignment angles of as little bit as three levels deserve to reason an annoying chirp and also increase the possibilities of the belt jumping its pulley. Inadequate belt anxiety adds to the likelihood of belt loss.

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Misalignment (and also the resulting noise) is most pronounced on brief spans in between pulleys. Diagnosis of much longer spans have the right to be difficult. A few degrees of balance out may not be noticeable to the naked eye. The usage of a laser alignment tool or straightedge can be helpful in finding these bit variations.