This just started on the way home from work tonight. I was caught a red light and stopped to wait for it to change. When I stopped I heard the engine not idling normally and turned down the radio to hear what's in the video below. The engine seems to be running ok, it's not overly rough, it still has plenty of power. No check engine lights or anything like that. Just the sound.

We bought it used at about 50k and it has about 98k on it right now. It's had Mobil 1 oil/filter changes every 5k miles since then. I haven't ever changed the serpentine belt and I was thinking about trying that tomorrow but I'm not sure if that will help. I thought belts normally squeal when they're slipping. My other thought is that one of the pulleys has some bearings going bad. I'm no expert, though, I could be way off. What do you guys think?

Video:

http://youtu.be/WYFiTNXGwhE

edit: I tried to embed the video but it doesn't appear to be supported here. If someone else knows how please feel free.

Sounds like a bad bearings in a idler pulley.

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2003 KJ Renegade, 5 speed, frankenlifted,Al's a Arms 4.5,Moabs 245/75/16 BFG KM2's, custom rock rails, full Mopar skids, Hella ff220 lights,Hd cooling,Front DTT,Riddler diff cover,Rola safari rack,Cobra 29 peaked & tuned.

Pastafari Alum, Pink shovel recipient

Well just went and loosened the belt. The tension wheels spin ok. There's a little noise on one of them but not bad. The a/c compressor was pretty hard to turn, though. I'm guessing that's my culprit. With the engine off and the belt remove I should have no trouble turning that, right? I think the a/c switch was on inside the car but that shouldn't matter with everything off.

Had the same problem on my 2002 last week. It was the compressor clutch bearing. Took care of it with a $33 replacement bearing from autoaironline.com.