Help diagnosing the elusive ghost supercharger sound

Hi guys,

My 08 TRD sport (V6 4.0L) has a whining sound coming from the front driver side engine bay. It sounds like I have a supercharger, but unfortunately when I pop the hood, there is no supercharger to be found. Leaving me on the hunt for this sound.

I have replaced my alternator (learned not to go fast into really big puddles on trails), my serpentine belt and two of my three idler pulleys. The third one (bottom one) looked like it was replaced within the last 3 years. It’s solid and doesn’t rock anywhere.

Having said all of that I still have this whining sound. I’ve searched and read that it could be the ac compressor or a bushing in its pulley. But my A/C works fine. I have to replace the blower motor under the dash as it doesn’t really work unless it’s on high or medium. But good none the less.

I have attached a couple videos for you guys to take a listen and tell me what you think. I want to try and fix it before snow starts hitting the ground here.

https://youtube.com/shorts/mDWd-c3R70Q?si=ojnK_Li6ESDXp6wX

https://youtube.com/shorts/jikLBoMMdbU?si=00kbxkfKpI4CNqSq

 

One quick check, pivot the tensioner on serpentine belt and wiggle your idler pulleys. See if any of them feel loose.

 

Get a mechanics stethoscope or a long screwdriver and start putting it on all the accessory components, then put it to your ear and you should be able to track it down pretty quickly.

 

I would try a stethoscope. If you don't have one, a really long screwdriver works too.

Beat me to it. Lol

 

Replace the tensioner and idler pulleys before one of them decides to explode when you’re 320 miles from home (ask me how I know). Edit: change the driveshaft u joints, too.

 

I replaced 2 of 3 idler pulleys. The 3rd one is fine. No play in it. Looks to have already been replaced. I will double check the tension, seems fine though, no play in it either. I’ll check the driveshaft u joints though.

 

right on thank you. By accessory components I assume you mean things like the ac compressor, alternator, the other items that have a pulley connected to them, yes?

 

My wife’s a nurse, she has a spare stethoscope will that work? Lol. Or do I need an actual mechanic one?

 

Might be more trouble than its worth for 8 bucks.

 

So I ended up replacing the third idler pulley. Had no luck. I was thinking it might be my ac compressor clutch. Figured it would be worth a shot at replacing that. But it was more expensive then a new tensioner assembly, so I opted to replace the tensioner assembly first as I knew it was bad. And that was the problem!

Runs like new. I wanted to update this post just incase it helps anyone else out in the future!