So, my '03 MCS has been displaying a whistle/whine from the engine bay at idle since I brought it home two weeks ago. My initial diagnosis was the serpentine belt, and that's on the way (or will be, as soon as Promini has them in stock), with the tensioner tool and an idler pulley for good measure. I based this diagnosis on the much more obvious belt squeal I hear from about 2000-3000 rpm on the first two or three miles of my commute. Now, though, I'm a little less sure it's belt- or pulley-related: the whistle/whine can be heard even after I've driven a while, but it's quiet enough that it's only really obvious when the car is idling and the door is open—any road noise at all drowns it out.

The sound's either coming from the passenger side of the supercharger or the belt area; assuming the pulley/passenger side of the supercharger is the front side, it definitely doesn't sound to me like it's coming from the water pump power take-off, presuming that's on the back. Still, though, I worry that the supercharger is in the process of grinding itself to dust, and that's obviously worrying. Assuming that removing the dipstick tube is simple, I'm going to do that and check that supercharger oil reservoir when I'm doing the belt and idler pulley, and either way I'll know in a week or so when I get the belt changed, but does this sound to you like a supercharger problem rather than a belt/pulley problem?

 

It wasn't the belt, since I put a new one on and it still makes noise. I wasn't able to replace the idler pulley, since the bolt is seriously stuck in, and leaning on the ratchet with all my weight wouldn't even get it out. It's going into the mechanic this week for diagnosis and repair.