Whirring Noise??

Hi all, I just joined the club and got an 09' TRD Sport with just over 100k on it. I bought it off the original owner who did basic routine maintenance on it, no upgrades so its completely stock. Prior to purchasing, I had it looked over by a shop and they said everything looked great except for low fluids and the need for an oil change. Long story short, I had all the fluids done and went on a short trip (roughly 300 miles). I went to drive the next day after getting home and noticed a whirring sound that correlated with the engines RPMs (wasn't there before), so when I accelerate the whirring increases with speed and is constant at idle.

My first thought was the power steering pump, but the power steering fluid levels are fine and the sound isn't affected by cranking the wheel. I took it to an oil stop for a second opinion and they think its just the fan being loud (not sure how confident I am in their opinion lol).

Any thoughts on what it might be or things to keep an eye out for??
Feel free to ask any questions, thank you.

 

Just had this on my 07 and it was a bad alternator. Same exact symptoms as yours.

 

Any tips on how to proceed or check if its the alternator? I know that a car can also make a whining sound when the voltage regulator is sending signals to the alternator to charge more than is necessary... Maybe that's what I'm hearing. The previous owner did upgrade the battery come to think of it.

 

MAKE SURE THE ENGINE IS COOL.
Pull the serpentine belt off. Start the engine. (Not too long, the belt also turn the water pump. But a few mins won’t hurt it)
If the noise goes away, it’s something powered by the belt. (Alternator, PS, AC, idlers , ect)
Spin each pulley and listen for a bad on.

If the noise persists, it’s engine internal. (Not likely)

 

Just for future reference: The voltage regulator is part of the alternator (internal).

I don't know of a modern manufacturer that has an external voltage regulator anymore.

 

Sounds good! I think its the alternator, I've heard you can confirm this by just unplugging the green plug running to it while the engine is running, and if the noise stops, you've found the problem. Any potential problems with unplugging an alternator while the engine is running?

 

No issues doing that on this model but some vehicles you don't want to.

My favorite tool for pinpointing noises is a long screwdriver but a wooden dowel or mechanics stethoscpe works well too.

 

Here is what my bad alternator sounded like https://youtu.be/PO-0PLNPVow

 

Did you do the replacement yourself? If so, any tips or issues with the serpentine belt removal, etc...?

 

Yep did myself. Ordered a replacement denso unit from rockauto. I believe there was a write up I am sure if you search for it you can find. Pretty manageable if you are somewhat mechanically inclined.

 

Yes there are plenty of how to videos online. It's not a bad job at all.