Early failure drive belt?

2009 Sonata; about 82K miles. Drive belt was replaced in July, about 6K miles ago, by Trusted Independent Mechanic in El Paso. Now, Trusted Independent Mechanic in DC area replaced it again because one of the belt’s ribs was falling apart. Attached photographs show a portion of the damage (which is only on that one ridge).

  1. Did that belt need to be replaced?

  2. What could have caused he damage? (Mechanic says pulleys look ok; maybe defective belt.)

If the pulleys are ok it would almost have to be a defective belt.

The possibility of a faulty belt exists simply because some people will return a belt to the auto parts store after having a change of heart. Sometimes the new parts are untouched; other times they may have been dinked with and a little damage inflicted. The parts counter clerk will likely refund the money and put the part back into stock with no questions asked.

If the current belt starts showing damage again then the pulleys need to be gone over with a fine tooth comb as there could be a nick or something in a rib on one of the pulleys.

+1 to OK4450’s post. Watch the new belt carefully.
Kudos are in order for catching the problem and following it up.
And thank you for the photos. It’s nice to actually be able to see an OP’s problem clearly for a change. We don’t often have that luxury.

+2 to @ok4450 and his comment. If any part of a belt fails…it needs to be replaced.

Thanks, that’s about what I figured. We’ll keep an eye on the new belt, and the owner (my son), after consulting the El Paso mechanic, has already contacted the corporate customer service of the parts store that sold the July belt. (“If they put it on wrong it can fail like that.” You bet!) If there is any interesting resolution I’ll post back, but that will be months from now. HNY

I’ve been rethinking my original post. I’m wondering if something like a tiny pebble might have gotten lodged in a pulley groove, especially the crankshaft pulley which is way down low and susceptible to flying objects. It wouldn’t take long for it to chew up a belt rib. Just a thought.

It seems as though it’s the same rib in all pics. I would check each pulley for damage. Also, belts can sit on a shelf for years and already be bad.

What they said. Inspect the pulleys carefully, otherwise it’s one of those oddball fixes, hard to explain, but necessary.

Agree with the others, probably the belt was defective out of the box. But it is common sense to check the pulleys for problems too. Even a small notch shaped knick will do this, as that notch will eat away at the pulley each time it coms in contact, over many miles driven. Note that inspecting the pulley isn’t as easily done as it is to say. Any time the engine is stopped to inspect the pulley, the problematic portion could be on a portion not visible to the inspector.

It would make sense to double check the number of groves, pullies vs belt, match too.

If after replacing the pulley, the problem re-appears, it could be a pulley alignment problem.

That specific damage is caused by the belt running off one rib on one pulley. It could be a pulley is out of alignment or the belt was installed wrong. The damaged groove was running on the outer edge of a pulley and not in its assigned rib. The belt may have eventually bumped/walked itself into the correct position shortly after installation, but the damage was done.