Interesting theory. Something else to consider... I think the sound is similar to what I first brought it in for, if not identical. So either the new alternator is bad AND is failing/defective in the same way as the old alternator, or something else is going on. Maybe power steering pump? I’ll put the stethoscope on that when/if I get a chance.

 

Mechanic replaced the alternator today with a new rebuilt unit. I'll be picking the car up in a couple hours.

The alternator rebuilder my mechanic dealt with (who obviously thought the alternator was good) thought I could have a failing battery, causing the alternator to overwork. Ever heard of that? My battery is 6 years old so is probably due, but that sounds fishy to me.

Fingers crossed.

 

Idea:

Take the serpentine belt off.

Start the car for a minute.

Did you learn anything?

 

Lol. That's a first. I've never heard that explanation. Looks like they put a bad alternator in. Definitely would of checked without the belt on the verify.

 

Update: The car ran great the couple of days I drove it earlier in the week -- noise was gone.

I am planning to replace the battery since it's 6 years old and maybe that has something to do with the first alternator failing? https://mechanics.stackexchange.com/...-an-alternator

Hard for me to believe the battery would appear healthy in every way and still cause alternator failure though. But might as well change it due to age.

Thanks for all of your input!