I was getting a squeak on one of 2 serpentine belts.
One is standalone AC belt and the other is the main belt.
I took off both belts to find the culprit. All pulleys and items that
are rotating sounded good and smooth.

I removed all 3 pulleys. The bearing are sealed, kind of.
There is a rubber flange/gasket that seals the grease in the bearing.
It's very easy to pop off the black seal and repack the bearing.

I'm sure these were the original pulleys on the X5.
The grease had hardened. And was not lubricating well.
I mopped up then sprayed with brake cleaner all the gelatinous substance.

I then repacked all 3 bearings and reinstalled the seals.
Bolted the pulleys back on and refitted the serpentine belts.

I removed the electric tractor fan for ease of this job.
After installing it into position, I cranked up the mighty 4.4.
Absolutely dead quiet.

This post is for those who can repack a bearing and save 80 bucks on a new set.
It is very easy to do and I spent a few hours and 13 cents on grease.

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2003 4.6is X5
2003 525it
2003 E53 X5 Standard shift