Resolved- Update: High pitched whining noise & burnt smell 4.0L

Sorry I worded that funny, that would seem to me the clutch is working normally, and the bearing is the issue.

 

And could anyone chime in with exactly how the AC clutch, compressor, etc..works so that I know exactly what is supposed to be going on when it's working properly. For instance, the pulley should be turning whether the AC is on or off, correct? And the compressor should only be engaged if the AC is on. I will try to do some research on that so i can get evreything straight in my head...just thought i'd ask here in the meantime as well. Going to watch a couple youtube videos now.

 

Oh, ok yeah that makes more sense with what i had in my head (with regard to how it's supposed to work). Thanks for your help. Sounds like the bearing may still be the issue. Hopefully this i a serviceable part, as opposed to needing an entirely new compressor.

 

One other thing to add: I found the following statement in another thread on the forum, but I believe they were referring to a 1st gen.

"When the AC is on, the bearing is not spinning like it does when the AC is off"

Could anyone clarify if this is true for the 2nd gen as well, and if so, does this shed any light on the situation considering the noise is present whether the AC is on or off?

 

Do worry about the above statement. Grab the center of the clutch on the AC when the engine is not running and see if you can turn it. If it turns just the bearing/clutch assembly, if not time for a compressor which is a known problem on the tacoma

 

I could be an Ahole stating obvious, but to remove clutch is not that much process, (one bolt if Iremember correctly) why not remove it and test it. Same with other items and idlers.
Did you check power steering pump ?
I would just take belt off and spin each thing by hand.

 

Yes, i have taken the belt off and spun each one of these by hand, but there was no discernable dragging/whining/play/etc in any of them. It seems that the noise is only present when everything is spun up to speed. I was trying to think of a way to spin each of these pulleys really fast with a drill or something, but from what i can gather some of the pulleys spin at upwards of 6k rpm and i cant figure out way to individulally spin them up that fast. If these trucks had multiple belts like the 1st gen, i could isolate certain things by removing the belts, but being that everything is run by the serpentine belt, i can't just remove one thing (power steering pump for example) as the belt no longer fits.

 

Ok far enough, how about record on your phone noise, try to get close to each while recording to get the sound level .. Post on you tube and link it here.

 

Ok, will do & thanks for the help.

 

I am very doubtful about it being the A/C.

Reason is the following;
1) owner can detect when A/C switches on and off. Means that the clutch is working fine -- otherwise the A/C is running FULL TIME.
2) The A/C clutch is a magnetic device on the end of the main shaft that runs through the compressor. When the A/C is "on", the clutch bearing is NOT turning. When the A/C is "off", ONLY the clutch bearing is turning.
** means that the noise could only happen either while the A/C is "on" or "off", but not both.

My guess would be alternator, since it is apparently related to speed.

 

i don't think we're ever really going to know until the OP brings it in and has it diagnosed. Not trying to be an ahole but I don't think the OP's skill set is high enough to help us diagnose the problem properly or to do the repair.

The video may help.

 

I'm sure you're right (about the OP), but video probably won't be any use. Just think, it isn't going to be a high quality video with multiple audio sensors, high resolution, and optical stabilization... its going to be a crappy cell phone video that's shaking all over the place and with noise cancellation cutting in and out trying to filter out the engine and squealing noise in favor of voice.

 

Alright well it is fixed...no more annoying whine. I did make a video & recorded the sound but as i was listening to it (before uploading to youtube) i couldn't help but think it just really stuck out in my head as alternator noise. So, I poked around with that stethescope some more and determined the sound was coming from...well, "everywhere". In other words, it was resonating through the metal parts of all of the pulleys and even the oil filter, believe it or not, so there were lots of false positives to sort out. Anyway i couldnt use the pulley bolt on the alternator like i had the rest of the pulleys because that bolt actually spins with the rest of the pulley. So i started to poke in around the motor part of the alternator while the wife revved the engine...and at that point it was very evident that was the source of the noise. Strange thing was when i did this with the truck at idle, i couldnt confirm the source of the sound.

To make a long story short, i replaced the alternator and she's good as new.

I really appreciate all of the help from everyone, saved me a lot of money from having to take it to a mechanic.

 

Good job, you get the cookie!