Ok guys. I need this nipped in the butt as of yesterday smh. 2013 GS 350. Horrible noise started off as a chirping noise. Serpentine belt? That was my first assumption. Went to buy a belt. Got it in hand. Lifted the hood. Now it's worse. Sounds like a million chirping birds on crack. I did the water trick to see if indeed it's the belt. Squirted water and poof! Noise gone!....of course not for long tho! Came right back within 2 minutes. At this point I'm like yea ok I'll change the belt. But as I look closer I see the alternator pulley not turning?! This cannot be normal right? In park haven't looked while in drive obviously lmao. I know it's a dumb question BUT I ask this bc maybe just maybe pulley isn't turning bc the belt is so jacked? Bc I'm having no alternator/power problems with the vehicle or anything.

 

Did you ever get this resolved? I am having the same problem right now, where there is a chirping noise upon start up and acceleration. It gets quite loud the harder I accelerate, and I would think it has to be one of the pulleys or bearings wearing out. I visually checked the belt and there are no cracks or signs of wear.

 

Thank you to this thread resolved my chirping in Reverse and Drive, cannot hear much while Park idle.

Was tough trying to determine if it was tensioner pulley or idle pulley, changed both idle pulley OEM and tensioner good after market. Idle pulley did have some play but didnt not resolve chirping.

When ahead with Denso replacement of alternator with decoupler and that solved the issue. There was a good amount of play in the decoupler pulley and cannot duplicate noise while the belt was off as it needed to be in gear and under load. Thank you to this older thread as I want to share with the community my resolution. Hope many of you have the simpler idle pulley issue without going the route of replacing the alternator.