Alternator Bearing Question **Noise Solved**

[nick0789]

I’ve been dealing with a whistling sound on cold starts coming from the engine bay. The sound increases as the RPMs increase but then go away at operating temp.
I spray everywhere there could be an air or vacuum leak to test and no engine response was noted. Then I pulled the belt and checked all pulleys and noticed the sound coming from the alternator in the video above. Am I looking at an alternator replacement?

 

[Doubeleive]

I’ve been dealing with a whistling sound on cold starts coming from the engine bay. The sound increases as the RPMs increase but then go away at operating temp.
I spray everywhere there could be an air or vacuum leak to test and no engine response was noted. Then I pulled the belt and checked all pulleys and noticed the sound coming from the alternator in the video above. Am I looking at an alternator replacement?

doesn't sound unusual, we need to hear this "whistling sound" normally those kinds of noises are a belt tensioner or AC pump
and the usual suspect for one that is initially noisy when cold and then not when warmed up is the ac belt tensioner, you could try taking that one off first and then do your cold start and see if the noise is gone, if so replace but note that sometimes......the noise may return even with a new one in short period of time, GM has since gone to a stretch belt now for the ac pump this may or may not be the reason why.

 

[Joseph Garcia]

^^ X2 ^^ check the A/C belt tensioner.

 

[nick0789]

Thanks for the info!

I should also add that when I replaced the water pump back in April I went ahead and replaced both belts, AC tensioner, and serpentine tensioner. All were GM parts.

I’ll pull the belt on the AC tensioner tomorrow morning before my commute and test it out. I’ll also try and get a clip of the noise when I leave work today.

 

[rockola1971]

While you are under the hood pull the main serpentine belt and check the bearing on the idler pulley when the bearing gets worn it whistles! The noise in your video is the commutator segments going across the alternator brushes. Completely normal.

 

[nick0789]

Here is today’s cold start. About halfway through the video when I move between the alternator and power steering pump you will get a better listen.

I still need to do a cold start without the AC belt tomorrow morning, though none of the pulleys up top sounded concerning or had any sort of play.

 

[MassHoe04]

It doesn't sound like anything serious going on there.

I could be wrong, but sounds like a hint of vacuum leak. Could be air leaking in from the air intake.
Check the air intake tube at the throttle body.
Maybe it got bumped or loosened during a previous service or on a bumpy road.
Loosen the clamp, make sure the plastic tube is seated properly and tighten the clamp. See if that does anything.

Possible, that the metal throttle body expands enough when heated up to seal off the slight leak...

Worth checking.

Good luck!

Merry Christmas and have a happy holiday season with family!

 

[Doubeleive]

Here is today’s cold start. About halfway through the video when I move between the alternator and power steering pump you will get a better listen.

I still need to do a cold start without the AC belt tomorrow morning, though none of the pulleys up top sounded concerning or had any sort of play.

to me kind of sounds like power steering, does the sound change if you turn the wheels?
another way to check is to take the serpentine belt off and then it start it up for a minute and see if the sound is still there.

 

[rockola1971]

That sounds like a needle bearing on its way out. There is a needle bearing in the rear case of your alternator that supports the rear shaft of your rotor.

 

[nick0789]

On cold start with the whistling noise, the sound goes away as soon as I slightly turn the steering wheel. When I stop trying to turn the steering we wheel the sound comes back.