humming near alternator 07 tacoma prerunner 4.0

im hearing a humming near or rather at the alternator, i put the stethescope on it and sure enough theres the hum, would this be my diodes going bad? also fan clutch blades are loose, does anyone think this go bad this soon?, i say this soon but the truck is 10 yrs old with 127k miles. btw im new to Tacoma World so im kinda illiterate to the lingo and what exactly to do concering the forums, in fact not even sure how to send this message, hope all is well with you people, ricola65.

 

I chased a noise near the alternator for a few weeks and it turned out to be the idler pulley to the left of the alternator. There's an excellent write up on this site for changing all the idlers if you search.

 

I recently had a similar problem. Idler pulleys and a few other changes fixed the problem:

https://www.tacomaworld.com/threads/2015-4-0l-oscillating-sound-in-park-with-a-c-on-fixed.502758/

 

i checked alll the pulleys but not with the serpentine removed, i put the scope on them while running and no humming, forgot to mention when i pulled the plug on the alternator while running the noise stopped, plugged it back in and the humming resumes again, looked at a youtube video and the tech claims its the diodes starting to go out, thanks for you feedback sir.

 

Yep sounds like it's the alternator/diodes
Mine was a squealing
https://www.tacomaworld.com/threads/2nd-gen-1grfe-alternator-rebuild-mud-cleanout.453757/

 

i listened to your video and mine sounds exactly the same, humming but not through the radio, appreciate you feedback Sandman614, have a good one.