Squealing Noise in the accessory area alternator, water pump?

[emmvette]

I have a squealing noise (fairly loud) coming from what sounds like the passengers side of the front of the engine. The noise is high pitched "whirring" noise. Definitely from something spinning as apposed to a drive train noise.
I noticed it the last time I drove the car and thought I had a vacuum leak, it was fairly quiet. Yesterday I popped the hood to listen to it and when I revved the engine the noise all of a sudden got much louder. I started it later in the day and it started off fairly quiet and then got noisy after 10 seconds of easy driving so pulled it back into the garage for some disassembly. Its loudest behind the alternator. I did a little search on the forum the other day and seemed like a few similar posts resulted in bad alternator. I removed the alternator and took it to a local electric rebuild shop and they tested it and it tests good and then they put it on there run stand and spun it up to 3,000 rpm which is faster than I'm guessing it spins on the car. I took it to them with the fan and pulley still installed and that is how they ran it. It made no unusual noise. He handed it back, no charge, and suggested I look for some other culprit and said it didn't need to be rebuilt, but he would do it if I wanted. I thanked him and took it home. "No need to fix what ain't broken."

At this point, is there a way to diagnose and figure out what is the problem, or do I just need to to randomly replace items? That isn't what I'd like to do.

I realize noise reverberates in the engine bay so its hard to track things down. And now, nothing is hooked up, so I'd almost rather pull the water pump now while I'm right there then to put things back together, start the car and then pull it back apart. I listened with a mechanic's stethoscope yesterday, but it didn't really help. I didn't try to put it down by the water pump due to the belts moving. Seemed like a bad idea.

Any suggestions for this novice mechanic wanna-be??? I do like working on the car, and its the only way I'll learn, but I want to be smart about my approach.

[Dynomite]

I would have thought it be Alternator.....could be Belt Tensioner Pulley....could be Water Pump......Could be very dry Serpentine Belt.

Alternator might test good but bearings are going. Did you check Play in Alternator Pulley?

Still seems like only item would be dry bearings in Alternator.
Squealing Noise seems can only be high rpm bearings or rotating items contacting where they should not be contacting.

Unless you are on wrong side of engine :p
Then AC.....or Power Steering.

I would remove serpentine Belt and see if the squealing reappears.
Drive the Z until squealing appears...then remove the serpentine belt.
That would isolate the issue quickly. Just do not run engine very long without water pump rotating :cheers:

[BigJohn]

Hope it is not a chain tensioner!

[tomcat]

I bet it's the alternator

Manfred E.:fahne:
91 #906

[emmvette]

I'm wanting to remove the belt next and run the car for 20 seconds and see if the noise is present. There is a lead to the back of the alternator to the - battery terminal. Is it Ok to start the car with the alternator removed (it is removed now)? I could tape the lead up so it doesn't arc. Or do need to re-install the alternator prior to starting?

[emmvette]

I bet it's the alternator

Manfred E.:fahne:
91 #906

Why do you think that if the alternator shop thinks its good? He sees them every day - I figure he would have a good feel for this.

[Dynomite]

I'm wanting to remove the belt next and run the car for 20 seconds and see if the noise is present. There is a lead to the back of the alternator to the - battery terminal. Is it Ok to start the car with the alternator removed (it is removed now)? I could tape the lead up so it doesn't arc. Or do need to re-install the alternator prior to starting?

You can fire it up without alternator but if squealing did not appear right away....you will not know if that is issue or not with alternator out of picture. I agree that inspection by alternator person would know if bearing is issue or not. You cannot run it very long without water pump rotating. You should be able to tell yourself by spinning alternator pulley by hand. Also spin the Belt Tensioner Pulley by hand.

In any event it would be interesting to fire it up without serpentine belt just to see.....you can run the engine for a bit if it is a new start......you say 10 seconds and you heard the squeal.....you can definitely run the engine for prolly at least a minute or more I would say as it would take a bit to heat up the coolant around the pistons even if no coolant is moving. But Temperature sensor of coolant is above that area in Injector Housing but still watch Temp gauge.

I drove my 91' two miles with water pump impeller spinning on shaft :p
Now that took some diagnostics :D
Temperature gauge said it was HOT so gauge was functional.
No Harm and no Foul.......Replaced Water Pump after lots of thinking it was water pump Air Lock and not water pump impeller.

[Paul Workman]

Couple things that might help:

With a water bottle, spritz some water mist on the belt while it is squeaking. If the squeaking stops for a moment or so, replacing the belt may be in order.

If the squeaking continues unaffected, prolly not the belt. A trick Marc Haibeck showed me was to remove the probe from a mechanics stethoscope & listen using the open end of the rubber tube as it is better to isolate some sounds, especially when a noise seems to come from anywhere and everywhere.
It works!

Oh, BTW... the LT5's crank (accessory drive) pully is quite a bit larger than the alternator's. So, it spins quite a bit faster than 7000 rpm - maybe 20,000+

[emmvette]

Thanks, Paul,
Read an old post from you and tried that prior to disassembly. No change.
I just finished removing the belt and ran the car for 30 seconds. Did a few revs which had caused the noise to elevate previously. No noise while revving now.

I spun all pulleys and they feel great, except the power steering. If feels fine, but has a little give and makes a slight noise like its two pieces. When I spin it by hand I can see it has runout. All others are perfectly straight. I don't have a dial indicator hear, but would guess its 1/16 - 1/32". Is that normal or acceptable?

The noise was without question behind the alternator so the power steering pump / pulley has not been on my radar.

[Paul Workman]

Thanks, Paul,
Read an old post from you and tried that prior to disassembly. No change.
I just finished removing the belt and ran the car for 30 seconds. Did a few revs which had caused the noise to elevate previously. No noise while revving now.

I spun all pulleys and they feel great, except the power steering. If feels fine, but has a little give and makes a slight noise like its two pieces. When I spin it by hand I can see it has runout. All others are perfectly straight. I don't have a dial indicator hear, but would guess its 1/16 - 1/32". Is that normal or acceptable?

The noise was without question behind the alternator so the power steering pump / pulley has not been on my radar.

Try the open rubber hose trick. That said, the PS pump pulley does sound like at the very least the pump needs to be replaced.

[Dynomite]

Thanks, Paul,
Read an old post from you and tried that prior to disassembly. No change.
I just finished removing the belt and ran the car for 30 seconds. Did a few revs which had caused the noise to elevate previously. No noise while revving now.

I spun all pulleys and they feel great, except the power steering. If feels fine, but has a little give and makes a slight noise like its two pieces. When I spin it by hand I can see it has runout. All others are perfectly straight. I don't have a dial indicator hear, but would guess its 1/16 - 1/32". Is that normal or acceptable?

The noise was without question behind the alternator so the power steering pump / pulley has not been on my radar.

So.......it sounds (no pun intended) like it has got to be the alternator?

When you say PS pulley has run out......you mean the pulley is not on the shaft perpendicular? That happens sometimes but does the pulley have any play when you pull and push on it? If not.....having a bit of run out just means the pulley was not pressed on the shaft perpendicular. I think my Aluminum PS pulleys have a bit of run out also but no issues.

[emmvette]

Try the open rubber hose trick. That said, the PS pump pulley does sound like at the very least the pump needs to be replaced.

I don't know what the open rubber hose trick is. I noticed last night the alternator and its fan were rubbing on the throttle body housing, so will lightly grind the housing and see if this cures the noise.

Will plan to get a new PS pulley on order shortly too.

[emmvette]

So.......it sounds (no pun intended) like it has got to be the alternator?

When you say PS pulley has run out......you mean the pulley is not on the shaft perpendicular? That happens sometimes but does the pulley have any play when you pull and push on it? If not.....having a bit of run out just means the pulley was not pressed on the shaft perpendicular. I think my Aluminum PS pulleys have a bit of run out also but no issues.



I found grinding marks on the underside of the TBH last night, so I will trim and reinstall the alt. OK, I think you are understanding what I'm trying to say. I bet you are correct, it may not be on perpendicular. There is no play when I push and pull. It seems solid like it should be.

[emmvette]

Well that was fun!! Guess what!? All mechanical parts are good. Whistling / squealing noise behind the alternator was a small plenum leak.

Kudos to Marc H. for some awesome telephone support to help diagnose. He really has a great mind for isolating and getting to the root of problems.

This morning we thought the alt was rubbing on the underside of the throttle body extension but found after a few simple checks this wasn't the case.

Anyway, its "fixed" for now with some high temp aluminum thermal barrier material I was using on my '68 for the firewall.

[onetinsoldier]

I had a squeal in mine , it was the clutch bearing in the compressor . It actually came apart and cut of the snout off the compressor at the snap ring and they don't sell the front piece of the compressor by itself , so you have to get an entire compressor or find a core !