Deflection pulleys are motor pulleys that are responsible for guiding and tensioning the motor drive belts. The engine drive belts are routed around the various engine accessories such as alternator, water pump, power steering pump and AC compressor in a specific way. The idler pulley is intended to provide another easily rotatable point for the engine belt to rotate so that the desired guidance can be achieved. Most motors use a pulley and a tension pulley, although some designs use more than one pulley. Over time, the pulleys will wear out and will need to be replaced. Typically, a broken pulley leads to some symptoms that can inform the driver of a problem.

1.
Visibly worn pulleys

One of the first symptoms of a problem with a pulley is visible wear on the pulley. Over time, when the pulley turns against the belt, both components start to wear out. This can result in visible scoring on the pulley surface due to contact with the belt. Eventually, the pulley and belt wears out until the tension is reduced, which can cause the belt to slip.

2.
Belt squeaks

Another common symptom of a possible problem with the idler pulley is the squeaking of the engine belts. If the surface of the idler pulley wears or the pulley gets stuck or seized, it can cause the engine belt to squeak as it rubs against the surface of the pulley. In some cases, a bad pulley can bind or slip and cause the belt to squeak the first time the engine is started. The problem will eventually worsen if the pulley continues to wear out.

3.
Bearing or pulley damaged

Another more visible symptom of a problem with the idler pulley is a damaged bearing or pulley. In more severe cases, the bearing or pulley can wear itself out so much that it breaks or tears and falls apart or seizes. This can disrupt the rotation of the belt and lead to all sorts of problems. A broken or stuck pulley can quickly result in a belt tear or, in less serious cases, the belt can fall off the engine. A beltless engine can quickly run into problems such as overheating and stalling as the drive belt enables the engine accessories to function.

LAST WORDS
Deflection pulleys are a common component on most road vehicles that may need to be replaced, especially on high mileage vehicles. All engine pulleys are very important for the overall operation of the engine as the serpentine belt and pulleys allow the engine to function properly after starting. If you suspect that your idler pulley is having a problem, have the vehicle checked by a professional technician

Source:
http://www.eliancars.com/2020/02/typical-symptoms-of-broken-or-faulty.html#more
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