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.

 

[corvette744]

Stethescope long screwdriver-long extention anything to touch the part while running and put to your ear.Always find my noise with a long screw driver you will know when you find it.

 

[nick0789]

on the off chance that it is the alternator, I went ahead and swapped it. I kept my NAPA receipt from like 5 years ago so it was free for me and a 15 minute job.
I’ll post an update tomorrow morning and go from there.

 

[nick0789]

Update: I still have the noise on cold starts.

To summarize,
- alternator replaced (preventative / it was free to me)
- no issues observed with tensioners or belts (all GM parts, installed new back in April)
- no other pulleys made noise or otherwise brought up concern
- slight movement of the steering wheel eliminates the noise, until I let go of the steering wheel
- Intake area sprayed with carb cleaner and no surging was observed
- exhaust was done back over the summer so I wouldn't imagine an exhaust leak (resurfaced manifolds, everything else was new from the bolts, gaskets, pipes, cats, O2 sensors, etc.). The exhaust manifold bolts were double checked for tightness.

I've narrowed it down to one of a couple potential sources:
- vacuum leak
- PS pump
- something else with the intake that I'm missing

 

[Fless]

Has a cold start been done with NO belts on it?

 

[Doubeleive]

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.

you might try flushing the power steering fluid if it hasn't been done.
all you need is approx 1 gallon gm power steering fluid, transfer pump (harbor freight or autoparts store has them cheap) and a bucket.
jack up the front end so both tires are just off the ground.
engine off- take the power steering cap off, stick the transfer pump hose in and pump out as much fluid as you can
refill with fresh fluid (as much as you pumped out)
put filler cap back on, start engine and rotate wheels full left/right several times, shut engine off
repeat process, until 1 gallon fresh fluid has been transferred in.
1 gallon is usually enough to give the system a good flush and you will see the difference from black looking fluid to clear looking.
some people take the lines off and do it that way but the above is my preferred method
doing this may or may not help the problem. certainly couldn't hurt.
in addition there may be some kind of snake-oil additive that may help, I have never used any but I think I have seen some at the autoparts store before.

 

[nick0789]

thanks for the idea! I was debating on doing a flush / drain and fill but was holding off on the off chance that I had to replace the pump. I’ll go ahead and get that done and report back.

As far as fluid goes do I need to stick with GM fluid or could I use a third party brand like Prestone or Valvoline, provided that the specs are consistent? I typically go with OEM fluids anyways but I can get third party stuff much faster.

 

[nick0789]

I went ahead and did the PS fluid flush. My old fluid was darker like a brownish color, but definitely not black or old oil brown. My brakes are a little firmer but I am also getting the hissing sound when I press on the brakes (I have hydroboost). Cold start this morning was the same as previous days in terms of the whistling noise.

I'll pull the belts tomorrow morning and see if the noise persists. How long can I let the engine run without belts and be okay with it? The whistling sound only appears when the engine has been running for 20-30 seconds, and I didn't think that you were supposed to run without belts much longer than that.

 

[Doubeleive]

I went ahead and did the PS fluid flush. My old fluid was darker like a brownish color, but definitely not black or old oil brown. My brakes are a little firmer but I am also getting the hissing sound when I press on the brakes (I have hydroboost). Cold start this morning was the same as previous days in terms of the whistling noise.

I'll pull the belts tomorrow morning and see if the noise persists. How long can I let the engine run without belts and be okay with it? The whistling sound only appears when the engine has been running for 20-30 seconds, and I didn't think that you were supposed to run without belts much longer than that.

if it's cold I would say you can run it safely for a minute, if it's really cold maybe a little longer
there's really no data on this just speculating, technically the thermostat doesn't even open until it reaches 180deg or so
I'm sure some engine builders have pushed the limits and may have more input.
I figured the flush was worth a try... same thing I would have done

 

[nick0789]

ran some cold start tests this morning:
(Shown in order performed)
1) No belts: no noise
2) AC belt only: no noise
3) Both belts on: whistling sound came through almost immediately

The sound is definitely the loudest on the driver’s side, which leaves me with the following potential sources (correct me if I’m wrong):
- Power Steering pump
- Hydroboost
- power steering line(s)
- vacuum leak (unlikely?)

How do I go about testing these two components?

 

[THarber]

Sounds like a/c clutch to me.

Tim