Pulley noise, whinning, which pulley is it ?

Pitch changes relevant to rpm''s in park or stopped in neutral.
I think it''s a pulley. Does anyone have info re. which pulley to
check, or what else could be the source of the problem ?

Thanks

Marcus used to talk about flex disc's making noise.... is it coming from engine bay or underbody ?

Didn't have my steth with me, but earlier today I popped the hood, and it sure sounded like whine was coming from the engine compartment. Tomorrow will be winterizing the boat, but if I get time, I will check out the noise with the steth and will post a follow up.

Thanks for the info, but have a "duh" question--what/where is the flex disk, and is this a big job. I do most of the work on my car--avoid the shop like the plague.

Sounds like the belt tensioner. Those howl when they're going out. Of course, it could be low on PS fluid.

Went and got my steth from the boat. Was using it there to ID a lifter prob.

Used in on car, and the whine is clearly coming from the idler pulley (MB says guide pulley.), not tensioner pulley, steeting pump, alternator, or fan.

Picked up part #0002020019, $31.20.
Will put it in tomorrow and post follow up.
Right now, am eating ice cream and watching war movies.

Thanks again for all of the help.

Sorry for delay in follow up.
Replaced pulley.
Problem solved.

Note: Using the "loosen clips & remove inner grill & and push radiator and condenser forward to make room to remove pulley bolt" technique, I ran into problem--not enough room to remove bolt unless the plastic pulley is broken away. My pulley did not fail and fall to pieces like others on this forum have. That was not my problem. My problem was that the pulley was intact, but was making too much noise, and had to be replaced. To have enough room to remove the pulley, using the above mentioned technique, I had to use a pair of big channel locks, and crunch up my noisy pulley into pieces, and then I was able to remove the bolt. After that ordeal, the rest of the job was easy.

A warning: Be careful after you remove the radiator retention clips, because it is easy to break the fragile plastic tabs that the clips mount on to. They stick out, and you can snap them off if you bump them or lean on them while you are working on the pulley. For such an expensive car, it has a lot of crappy overly fragile plastic parts.