JoeOh

I replaced the two idler pulleys and the serpentine belt. Made sure the belt is tight enough (by twisting the longest exposed part 90 degress and it goes no more, and 1/4" to 1/2" deflection). Everything looked great, started up the jeep and it ram like it should.....for about 60 seconds.

Before, This "chattering noise" started 10-15 seconds after startup from a overnight-sitting cold engine. Now the same noise is happening but much later than before.

I read that there may be a "loud air pump" that makes a racket on ice cold start-ups but I don't know.

What could this be still"? I checked all the other pulleys and they are spinning as they should, quiet and feels like they are grease filled. Thanks-

JoeOh

Either I'm not explaining what is going on well enough or this must be a weird problem.

Also, I did now notice that the power steering pump pulley has a very slight wobble to it. I'm guessing that means a new PSP is in my future as I am guessing that the bearings are going bad. I hope this is the source of the noise, but who knows.