Belts & Hoses

When a vehicle shows up for service with a “noisy belt,” the usual assumption is that belt is trashed. But that is not necessarily so. It’s easy to blame the belt when it makes noise, but in reality the belt may be just fine - and trying to do its...


 

TENSIONER INSPECTION PROCEDURES

Gates officials offer these methods for inspecting the tensioner.

- With the engine running:

1. Observe the tracking of the belt as it revolves around the pulleys. Pay attention to the flat idler pulleys, especially on the tensioner arm. The belt, for the most part should run true to the center of the pulley. As noted previously, if the belt is “off tracking” on the tensioner arm pulley, pivot bushing wear is the likely cause, and it is allowing the arm to pull away from the base. Although you might not be able to see this separation, side scuffing of the belt or chirping noise will often confirm this. 

2. Observe the tensioner arm movement as the belt travels over it. There should be a gentle arm motion as accessories turn on and off (such as the A/C compressor clutch engaging and disengaging). If the tensioner arm is bouncing or hammering it has already failed and must be replaced.

- With the engine off:

1. Remove belt and visually inspect each pulley. Running surfaces must be in good working order, free and clear of dirt, grease and grime. Clean all pulleys to provide an optimum gripping surface and minimize slippage of the new belt. Any residue oil on a pulley will coat the new belt as soon as the engine is started and the failure process will start over again. 

Before reinstalling any used belt, check the belt for wear using the belt wear gauge. Remember, a belt can only perform as well as the other parts of the system will allow. Inferior pulley quality will shorten belt service life and reduce system efficiency, resulting in comebacks at a later date. 

Inspect the outside of the tensioner for rust bleed seepage coming from inside the tensioner. This is normally an indication that there is metal-on-metal wear on the inside of the tensioner and a clue that it is failing from the inside out. Replace immediately.

2. Spin the pulleys. They should spin freely without any undue bearing noise. Check for any grease seepage or smudging around the pulley bearing.  

Seepage is an indication that the bearing seal has been compromised and grease has leaked from the bearing. The pulley bearing will begin to make noise and eventually seize if not replaced soon.

The proper way to repair a tensioner pulley failure is to replace the entire tensioner, rather than just the pulley. The tensioner is built as an integrated device, and the internal components have absorbed as much wear as the pulley. “Don’t risk a comeback by leaving aging parts on the vehicle,” advise the officials.

3. Use a wrench to cycle the tensioner arm through its complete motion path. Do this a minimum of three times. Feel for spring tension along with a fluid motion throughout its arm path. Any sticking or notchy movement may indicate a problem with the spring or pivot bearing. While cycling the tensioner feel for base arm separation, which is the result of pivot bushing wear. The tensioner arm should not rock from side to side. This looseness at the pivot bushing will cause pulley misalignment (side abrasion on a belt).   

4. The “Spin Cycle” test, mentioned previously, is a recommended starting point for checking a tensioner for potential problems. If at any point during the test concerns are found, it is highly recommended that the tensioner and belt be replaced immediately. “Failure to do so will provide the possibility of repeated comebacks, lost profits and a less satisfied customer.”

 

LET US SPRAY

The Spray Bottle Test is a simple method that can be used to narrow the search for the cause of serpentine belt noise and save much valuable repair time, say Gates officials. For safety sake, this test should only be performed by a professional technician, who is familiar with working on or near an operating engine.

Use a spray bottle filled only with water to quickly identify whether the belt noise is caused by a tension or an alignment problem, which will direct a technician to the cause more quickly. Any other liquids or additives will contaminate both the belt and the pulleys.

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