2000 civic SI. 30,000 mi ago, the A/C idler pulley was making a high pitch noise. Especially loud in the morning after a humid night. I changed it out when I did my Tbelt change. Now the noise is back and it's definitely the AC idler pulley. Is this a common problem on the B series engines? Anyone else have the same trouble?

 

Are you possibly over-tightening the belt?

 

+1; this is not normal

 

yeah im going to go with over tightening of the belt OR if perhaps your AC compressor pulley is slightley bent one way and putting an uneven stress on the idler pulley

 

FYI, I changed out the A/C idler pulley 10,000 mi ago and it fixed the problem. It was a bad A/C idler pulley bearing. Belt wasn't overtightened, it was just a bad part. Possibly the dealer who did the work (along with the T/belt) just sprayed some silicone into the bearing to make it quiet for a few thousand miles. BTW, I hate dealers...they charged me for a new part!

Cant get anything done right unless you do it yourself nowadays!

 

When having parts replaced at a shop, you have the right to ask to keep your old parts. This is good evidence (though not absolute proof) that they actually replaced something.

Generally once a bearing gets so bad that it makes a enough noise to be audible from the driver's seat, relubricating it with anything is not going to help.