Unknown whining sound from engine bay

Can you please tell me what this might be? It started a few weeks ago and tonight it got louder. I have a 2007 4.0 2wd auto. It appears to be loudest on the driver side. No check engine light so far. The sound increases and decreases with RPM's. No change in sound when turning wheel and PS pump fluid is full and has been for a long time. No increased cranking time when starting.

https://youtube.com/shorts/ODu417iOq3s

https://youtube.com/shorts/PO-0PLNPVow

 

Sounds like an alternator, does it change with electrical load?

 

Yea I have been watching some videos and a bad diode causes a very similar sound. I haven't really tested any extra load on it. I don't have any accessories hooked up like extra lights or anything. I know it doesn't change when I turn the AC on and off it just goes up and down with my rev's.

 

I meant blower and headlights on high vs off.
Just listening on video sounds like a failing alternator but it could also be an idler bearing, you can use a long screwdriver, wooden broom handle, or mechanics stethoscope to pinpoint the noise just be careful around moving parts.

 

Ok I just went outside and starter her back up and had my dome light on, radio on, AC full blast, high beams on and didn't notice a difference in sound. It just goes up and down with the rev's still.

 

I had the same noise in my son's 2007 Tacoma. Replaced the alternator/serpentine belt and noise disappeared. He drove to college last week from Boston to Ohio and had zero problems with his new ride. Only thing left now is seat jackers (he's 6'2). Semester break we'll get it done. Enjoy your day.

 

Update. It was the alternator.

 

I was gonna say, 99.9% alternator. Mine had the same sound. Easy to diagnose, just unplug the 4 pin connector on the alternator while the truck is running, if the sound goes away. boom theres the culprit

 

I love this group like I had so many problems and all you guys have really helped and saved me a ton of frustration and money!

 

Thanks for the update

Glad you solved it.

 

Yea def glad it's over. I also use to have some slight vibration on the highway I thought was torque convertor shudder, but it went away after this. I wonder if the trans computer wasn't getting the correct voltage and causing issues.

 

The fact that your whine was the alternator is no surprise to me… the vibration has be intrigued though.

 

Yea it feels like possibly torque convertor shudder but it only happens at night around a certain stretch of highway. I can tell it's coming on because the pedal will feel less responsive and the wheel will shake. The truck still tracks straight and usually if I just apply the brake with my foot still on the gas it will instantly stop it. Just curious why it only happens at night on the way home from work.

 

check here... almost sounds like the same problem
https://www.tacomaworld.com/threads/whirling-noise-under-hood.773100/

 

Thank you. That is also my thread. I'm going to a drain and fill on my transmission to see if it helps.

 

It can be the idler wheels too. I have replaced the upper one, the lower ones are on my bucket list.

 

That being said - is there an upgrade for the alternator i.e. higher amperage? 4.0 V6. I think mine still has the original one, something else to put on my bucket list.

 

The tow package V6 has a bigger alternator

 

Yeah, pretty sure I have the factory tow package. I will wait until it blows up to replace it.

 

Mine lasted a month making that noise before I just got tired of it and replaced it.