Pulley Whine - Idlers?

Hey all, my '11 4.0L has a whine in the front end that is RPM based and not dependent on AC or steering input. I took a couple videos and i'm curious what other's thoughts are on the level of wiggle/friction in these pulleys. There's one pretty obviously bad one but should all of these be replaced? Engine has 202k miles on it and i don't know if they were ever replaced.

Video of the whine here, seems to be louder from driver side up top, harder to tell from underneath. - https://www.youtube.com/shorts/jHIS27Cq4Sw

So far I've tried the following for diag:

-Unplug the alternator while running to eliminate possible diode whine i've read about - NO CHANGE

-Remove the serpentine belt and run without the belt for a few seconds - Peace and Quiet, Noise is gone. Confirming the noise is coming from a pulley.

While I had the belt off I noticed one idler very obviously high in friction, but didn't really feel too grind-ey or bad, and didn't wiggle a lot, it was just a very noticeable lack of rotation.

Video here, bad pulley at about 25 seconds - https://www.youtube.com/watch?v=ICpLuCNk_XU

There is a second pulley that has a little more wiggle than the rest but seems to spin smoothly? - Video here, wiggly pully at about 40 seconds. The high friction pulley is also at the start of this video. - https://www.youtube.com/watch?v=pploqA_umOU

 

At 200k if it were my truck I'd replace them. Other than the tensioner itself, replacing the idlers isn't difficult or very expensive. Splurge and replace your belt while you are at it if the belt is old/worn.

 

Just picked up a belt and idler kit off ebay for ~$200. I dont remember the exact dealer quote but i know it was >$200. Gonna start with the 3 idlers and belt and see how much that cuts down the noise. The tensioner pulley felt OK so I'll piecemeal that one in on my next parts order.

 

with 200k and not knowing the history, even thinking about this makes no sense IMO. Just replace all of the idler and tensioner pulleys and the belt.

Years ago, I had a bad bearing minor squeal type noise that turned out to be a bad belt on my Tacoma. The pulleys were all fine, but it sounded like one was bad, but the belt was the issue.

 

I tried this and it seemed to work. When the belt in squeaking. You can take a squirt bottle of water and squirt a little on the belt. If the squeak persists then it's like a pulley if it goes away it's the belt.

 

Unless the bearing in the tensioner pulley is in really primo condition, you should replace it while you’re in there. You can just buy a new bearing for it. If you have a block of wood, a socket set, and a hammer, that’s enough to let you pound out the old bearing and install the new one. I use the old bearing to press the new one in so that I was sure I was only applying force to the outer race of the bearing. Easy Peezy so long as you know that the tensioner pulley bolt has reverse threads.

Be sure to spin the alternator, air conditioner, water pump, and power steering pulleys by hand to check for odd noises before putting the new belt on.

 

Ok, yeah I have read about people doing that instead of replacing the whole tensioner assy. Is just the bearing sold as an OEM part or where can I find that?

 

I made up this diagram for myself (building off someone elses that had the gates #'s) a couple weeks ago while I was replacing stuff and comparing prices and reviews and stuff. You can press the NACHI bearing into the OEM tensioner pulley but if you want a new pulley you can get the Febest and replace the cheap chinese bearing with the Nachi one, both from Amazon. I ended up getting an OEM tensioner for 100 bucks and unbolted the pulley and swapped it over since it was gonna be like 65 or 70 for the febest and nachi combo anyways, and I plan on keeping the truck a long time so now I have the tensioner assembly when the time comes for an extra 30 bucks. Swapping all the idler pulleys was super easy though, just make sure you remember the tensioner one is left hand thread.

 

Yeah with the mileage I think using the OEM pulley makes the most sense, a few extra bucks to have a tensioner on hand in case it ever fails. Plus that's using OEM parts.

FWIW I felt and listened to the other pulleys (alt, AC, PC) and none sounded bad or felt rough so I'm hoping I get out of this easy with just idlers and tensioner.

 

pull the belt
check for smooth rolling of bearings
if one is gone, the rest will go soon

I do tensioner and idlers with a new belt so i know its good for another 100k

OEM belt lasted me almost 200k

 

Finally got around to throwing the new idler pulleys and belt on and ITS QUIET!!! So satisfying to finally not hear it whine, haha. I didn't end up replacing the tensioner pulley because the dealer didn't have it in stock but I probably will the next time I can sneak it in to a parts purchase. For now though, success.