Engine making high pitched whistle or whine
 

2002 Voyager 2.4 with 125K
Just starting making this high pitched whistle or whine, coming from the right side of the engine where the drive belts are. I first thought it was a vacuum leak, but it comes and goes. Pitch increases with RPM. The water pump was replaced at 90K with the timing belt plus drive belts, I can't remember what else was replaced with that. It does not seem to be the alternator, I used piece of hose to the ear to try to locate the source of the noise.
It makes the noise while driving and while idling in park.
A/c on or off makes no difference.
Turning the steering makes no difference.
With the engine at idle the noise starts at a lower pitch and increases pitch and then goes away for about 30 seconds, then starts the cycle over again.
Is there an idler pulley? What else could it be?

"Turning the steering makes no difference."

Could still be the PAS pump, perhaps?

is teh noize more like a chirp than a whine? that would most likely be the idler pulley... not fun to change

The noise was a even pitched whine, kind of like a whistle from a vacuum leak.
Anyway I checked my PAS reservoir and the fluid level was midway between the 2 upper marks, filled it up to the top mark and the whine went away.
Now just to figure out what is making a tinny rattle on the right side of the engine, it sounds like a washer rattling on a loose bolt.

Uh it was not the PAS fluid level, noise is still there.
I'm suspecting the alternator. I poked around with a mechanic's stethoscope and get a screech from the alternator.
How can I verify that before I buy another one?
Replace alternator or replace bearings?

sure it's not more like a chirp? look at your belt and idler tension pulley, if you haven't already...

It's a very constant whine and not a chirp. My alternator is not charging at the correct rate as well, so that's another sign that it is on its way out.

Well after pulling things apart it turns out to be the idler pulley. It sure is past its useful life and one heck of a thing to get out.

My tensioner was pretty cockeyed. I changed it, the pulley and the belt last December. Before that, it would chirp after about five minutes running.

I'm getting ready to do the valve cover gaskets and new wires and plugs. You are right that things are hard to get to on these, no wonder the dealership charges so much!

Mine was sounding like a swarm of angry bees, it was getting ready to bite me at any moment. I have done new plugs and wires. Yesterday I noticed the valve cover gasket leaking, so that is on my list... after replacing front shocks (back already done) and steering rack + tie rod ends.