Is the squeaking noise I'm hearing coming from the "idler pulley"?

Asked by Apr 28, 2014 at 03:35 PM about the 2003 BMW X5 4.4i

Question type: Maintenance & Repair

I recently had a new alternator and brakes put on my 2003 BMW X5 (4.4i).  There is now a squealing sound that happens only when the car is in motion.  This issue presented after the alternator was installed.  I was told it was the brakes so I had them replaced but the noise still persists.  There are no lights or indicators of any low fluids or any other mechanical issue.

Could it be the idler pulley?  Would this have been damaged during the installation of the alternator?

2 Answers


noise that only happens when wheels are rolling should indicate the sqeak is related to the wheels turning, listen to see which side the sqeak is on and then jack up that wheel and turn it with your hands and that should help locate what is rubbing.

Tom Demyan

Best way to find out is remove the serpentine belt and spin the pulleys by hand. Are they free spinning and make noise? Then time for a new one, they usually need replacing around 80K. Check idler pulley, tensioner, etc. Inspect the belt while your in there too.

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