I've trying to figure out a problem with the one of the driven accessories on the front of the engine that's making a groaning noise that comes and goes. Hard to describe the sound, but it's like a low pitched squeal or groaning that is sometimes intermittent.

AC clutch will come on and off with no change in the sound, so I know it's not the compressor. On one of the idler pullies (below the tensioner), I see the belt kind of wag back and forth, almost as if a pulley nearby weren't 100% in line.

It's really bizarre because the pulleys in the vicinity (tensioner pulley, crank, alternator) seem to be spinning nice and true. The noise seems to come from that side however. Now strangely, on the opposite side, the idler pulley over there almost seems like it's rocking back and forth. But I observe no wagging back and forth of the belt or other oddities on that side.

Any usual suspects for accessory belt issues, or noises from this area? Any help or suggestions would be much appreciated.

 

its usually one of the small idler pulleys. i have/had a bad one on mine. both spun true. you need to remove the belt and see which one is harder to spin.
when i sealed the front cover i took off the small one, pulled the rubber seals on the bearing, packed it with a good grease put the seals back, and re-installed it. been fairly quiet ever since.

 

My truck has 111k miles, and I've had the tensioner and a idler fail in the last year. The idler failed while I was on the interstate and if I didn't get lucky it would have stranded me. So I went ahead and replaced the other idler shortly thereafter.

BTW, I repacked the idler that failed a month or two before it died. I'm convinced the fresh grease just masked the symptoms until the bearing seized. It was dead silent til it threw the belt. If you do choose to repack, you are supposed to use special high speed grease that you'll likely have to order. At the time, I did some research, decided just to try regular high temp grease, and it screwed me.

So frankly I'd replace the idlers and tensioner just because they're old. And be sure to replace the entire tensioner, the spring will eventually weaken and cause problems.

The cheapest places I've found to get parts are ebay, amazon, and rockauto.com. As I recall the driver's side pulley was kind of expensive.