Timing belt needs replacement

Tiny
JSGJJ1@AOL.COM
  • MEMBER
  • 2004 TOYOTA COROLLA
  • 2WD
  • AUTOMATIC
  • 92,000 MILES
My car dealer is has been telling me for a year that my timing belt needs replacement. I was reading that a 2004 Corolla gets the chain belt and not the timing belt. He told me that when the car turns on and if I hear a chirping noise, that is the sound of your belt needing change. Is this correct?
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Thursday, February 13th, 2020 AT 2:43 PM

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Tiny
CARADIODOC
  • EXPERT
It sounds like you're confusing two different parts, or, it sounds like the person at the dealership is confusing two different parts. This is a classic example of the unintentional miscommunication between service writers who often never were mechanics, but they're trying to take what they heard from the mechanic and translating it into something they think you will understand.

Your engine uses a timing chain instead of the more common timing belt. Timing belts do require periodic replacement. Many smaller engines are of the "interference" design in which if that belt breaks, some of the valves will be hit and bent by the pistons as they coast to a stop. That turns a maintenance timing belt replacement into a very expensive valve job. All car brands have some interference engine models, but these are used much more often on import cars.

Timing chains are less likely to break, but they require periodic adjustment.

Timing belts rarely cause a squeal. If they do, it is because of some other underlying cause that is going to cause the belt to break soon. That includes worn idler pulleys, tensioning devices, and on many engines, the water pump. All manufacturers will specify the time to replace their timing belts. Those commonly are from 100,000 to 150,000 miles. One notable exception was for Honda's. They recommended the timing belts be replaced every 75,000 miles, and they typically broke at 65,000 miles resulting in very expensive engine repairs and a lot of unhappy owners.

The belts that commonly squeal are the "serpentine" belts that drive the generator, power steering pump, and sometimes the water pump. The squeal is caused by the belt sliding sideways across a pulley as it goes around it. That is caused by that pulley or the one right before it is turned or tipped due to a worn internal bearing or wear to the pivot point on an arm the pulley is bolted to. When you have that squeal, it is more important to address the cause than it is to just replace the belt.

The other thing we look at during any routine service is the number of cracks across the ribbed side of the belt. Those show up when you look at the belt where it goes around a smooth pulley. Unless the manufacturer specifies otherwise, the standard is we're allowed up to one crack per inch. My suspicion is this is the belt they're referring to. They don't break real often, but that's because they get replaced at regular intervals. At the mileage you listed, it's about time. This isn't a very expensive job.

Here's links to some related articles that will provide more information:

https://www.2carpros.com/articles/how-a-serpentine-belt-works

https://www.2carpros.com/articles/how-a-serpentine-belt-tensioner-works

https://www.2carpros.com/articles/replace-serpentine-belt
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Thursday, February 13th, 2020 AT 4:04 PM

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