Whistling Sound From Alternator?

[revans]

I put a new alternator in my 2003 GMC Yukon (5.3L Vortex engine). I loosened the air snorkel/tube to the throttle body during that process. Now there is a whistling sound coming from somewhere in the engine. I tightened the hose clamps as tight as possible and sprayed water at connection points to see if there was a change in idling. There was none. Is the sound from a loose air tube connection or from the new, not rebuilt, alternator?

 

[Fless]

Pull the air tube off where you had it off before, and make sure the flexible part isn't deformed. Reinstall.

Remove the main serpentine belt and run the engine for a short minute, to see if it's something in the serp belt line, or something else. You can use unlit propane to search for vacuum leaks; it's much better than water.

 

[Marky Dissod]

That whistle is more likely from the PCV, or from the AC compressor. My idle also has a whistle that kids hear better than adults.
Someday I'll stop noticing it while my nephews keep asking why I haven't fixed it.

 

[revans]

I did just have the AC recharged because it was low on Freon. So Occam's razor says it must be the AC. Right? So I called the service writer at Christian Bros. and he told me to bring it by so he could give it a listen. He and a mechanic checked it out and determined the sound is coming from the alternator.

So this is really interesting. I installed a new alternator that made a whistling noise. Took it to the retailer who put it on a test machine while I watched. No whistling sound and the alternator passed inspection. I asked for a replacement alternator exactly like the new one. They gave it to me and I installed it. The whistling sound was still there. The bottom line is both alternators came from a bad batch from the manufacturer.

 

[LsHart]

So it's fixed?

 

[revans]

So it's fixed?

Actually, yes. It is fixed. I think, but there's a twist to this story. I bought yet another alternator, this time from Auto Zone. The whistle did not go away! That's three alternators; two from a supposed bad batch and another form a completely different manufacturer. I called the service writer at Christian Brothers Automotive (CBA) and loudly complained. They asked me to bring it back in; which I did. Their analysis was that it still was indeed THE ALTERNATOR!

They checked the pulleys for sound. They checked the alternator for sound, and the noise still came from the alternator. Their explanation is that for that model Yukon, all alternators are going to make that same sound. Apparently, modern alternators are manufactured differently. Do I believe them? Yes, but reluctantly even though my own ears tell me that the culprit is the alternator. CBA always done good work for me. So I will go with this new limited lifetime warranty alternator from Auto Zone with an annoying whistling sound, until it breaks or dies of old age. What else can I do?

 

[Marky Dissod]

I will go with this new limited lifetime warranty alternator from Auto Zone with an annoying whistling sound, until it breaks or dies of old age. What else can I do?

Try to somehow attenuate the airflow through the alternator? Whistling by definition is an airflow issue.

 

[West 1]

Engine running, mist the belt with water. Noise gone it is a belt issue.

 

[Doubeleive]

Actually, yes. It is fixed. I think, but there's a twist to this story. I bought yet another alternator, this time from Auto Zone. The whistle did not go away! That's three alternators; two from a supposed bad batch and another form a completely different manufacturer. I called the service writer at Christian Brothers Automotive (CBA) and loudly complained. They asked me to bring it back in; which I did. Their analysis was that it still was indeed THE ALTERNATOR!

They checked the pulleys for sound. They checked the alternator for sound, and the noise still came from the alternator. Their explanation is that for that model Yukon, all alternators are going to make that same sound. Apparently, modern alternators are manufactured differently. Do I believe them? Yes, but reluctantly even though my own ears tell me that the culprit is the alternator. CBA always done good work for me. So I will go with this new limited lifetime warranty alternator from Auto Zone with an annoying whistling sound, until it breaks or dies of old age. What else can I do?

mmmm, I would try a new serpentine belt, just for shts n giggles.
or for trial and error, take the existing serpentine belt off, leave the ac belt on, start it for a minute and if the whistle is there that rules the ac system still in. Or like mark said air flow

 

[strutaeng]

$8 stethoscope from Harbor Freight is gonna be your friend here. Could be a bearing on the alternator.Poke around with that probing rod and take a listen. I have pinpointed numerous items that make sounds with that tool including a tensioner on my 1999 5.3 engine.

Probably the most challenging was our 2013 Chrysler minivan. I replaced the thermostat on it, but to purge the air out, you have to loosen this bleeder screw while it running. That dumps air/coolant into the belt, which is a crappy design if you ask me. Well, a few months later the belt starter squealing. I blamed it on the coolant spill. I replaced the belt and sent it. Weeks later squealing came back and was worse.

So I go down there with my stethoscope and couldn't find any bearing, idler or anything making the sound. Everything was whisper quite. I was however able to see the harmonic balancer wobbling horribly! Apparently, it's a common issue on those engines around the 100k mark. The metal pulley literally "walks off" the rubber portion, then starts wobbling and making the belt squeal, eventually shredding the belt if left unattended. I was shocked, I'm used to out LS harmonic balancers lasting forever, LOL.

Edit: It's actually $8.99 here. https://www.harborfreight.com/mechanics-stethoscope-63691.html

 

[West 1]

There are two Harmonic Balancer rebuilders in No California. Both located near Redding CA. Damper Dudes and Damper Doctor. Both can do a very nice rebuild of your OE damper. Or just get a new OEM unit.

 

[mortten]

2 boys have an 03 and an 04. They both whistle.

 

[LsHart]

Never heard my tahoe whistle. But that's just mine. Has an aftermarket intake tube on it. Not saying it's the same but, ford explorers had a whistle and it was the air box making the whistle noise. I know it's not the same! Besides that I know that sucks

 

[revans]

2 boys have an 03 and an 04. They both whistle.

Now that's interesting, and makes me feel a bit better, but not much. LOL

 

[LsHart]

A video would help. Just for us to hear.

 

[Doubeleive]

I have had several none whistled, that would be resolved one way or another