What could cause a high-pitched belt whine from the idler pulley?

[Chloe.C]

My 2016 sedan has started making a faint but constant high-pitched whine that seems to come from the front end whenever the engine is running. It doesn't change with engine speed or go away when I turn the steering wheel, but I can hear it clearly at idle. I'm worried it could be a sign of a failing accessory belt component, maybe the idler pulley or the tensioner bearing starting to go.

[Mia20]

I had something like this a while back. A faint high-pitched whine from the front at idle turned out to be the tensioner bearing on the belt drive. I swapped the belt and the tensioner, and the noise disappeared after a short drive.

[AlexanderXM]

That sounds reasonable to check. If it keeps coming, try listening for other clues. Alternator bearings can make a steady whine that doesn’t care about steering or RPM. A quick shop check or using a stethoscope on the belt area can tell you if a pulley is seizing.

[Kevin71]

Could be something else, like a worn pulley or a failing water pump bearing. Those can show up as a constant tone too. Do you hear it more on cold start or after it warmed up?

[Kevin_L]

One time I chased a similar noise and it turned out to be a loose splash shield rattling at idle. Not likely, but it’s easy to check. Wiggle the belt covers, look for loose brackets or shields, and see if anything taps or rubs when you rev gently.