I replaced my 2014 Serpentine Belt 2,000 miles ago. The original belt was still going strong after 196k, but it was time to replace for peace of mind.

All the components looked fine when I replaced it with the exception of the upper idler which was replaced using an OEM replacement.

Today, I had the hood open and just so happened to notice some fraying threads visible on the belt. Photos attached.

I'm a bit concerned about this and will probably try to replace/warranty it with McGeorge Toyota where I purchased the 90916-A2015 belt.

Can anyone else with experience let me know if this is a real concern or not.

Thanks

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I don't remember any threads on my OEM belt I replaced few years ago. It is hard to see how those will survive running backside on idler an tension pulleys. I'm guessing that thread is part of manufacturing and does not matter after the belt is cured.

Agreed. My OEM belt didn't have any stitching like this. It was part #99367-H2150 which has now been replaced by Toyota with 90916-A2015.

The belt pictured with the stitching is the OEM Toyota 90916-A2015. I ordered a replacement to put on and I'll warranty this one with Toyota. For now, I'm just limiting my use with this vehicle until I can replace it.

I contacted Bando for a definitive answer. They’re the ones producing these made in the USA OEM belts for Toyota.

Here’s the engineer’s response:

“That fraying will eventually wear off. The fabric is only stitched to hold it in place during the building of the belt. The rubber impregnated fabric is cured to the backing of the belt so the stitching isn’t relevant to the functioning of the belt during use.

Most auto manufacturer’s have transitioned to a rubber backed belt without any fabric backing. As I mentioned on the phone, our aftermarket belts do not have the fabric backing.”

I bought a second belt from Toyota and it’s obvious the same stitching will have similar results. Glad there’s nothing to worry about.

Hopefully this might help someone else.

Good to know. I've done my belt like 3 or 4 times and have yet to see anything like this.

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It's a bit weird for sure. He said most people would never get so lucky to have the belt stop at exactly the right point where it's visible that stitching is wearing out.

Apparently, Toyota OEM spec requires that fabric layer. They make the same belt for the aftermarket without it.

Not a 4runner but I'm doing the belt (oem belt) on my wife's Camry this weekend and it doesn't have any stitching.

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Most belts don't have the fabric backing. That's just an OEM spec thing with Toyota.