High pitch squealing, pitch change in idle, low sp

[ken]

I hear a high pitch squeal when the car is idling or moving slowly through drive-through. The pitch/tone/frequency changes when I move from neutral to drive.
The noise goes away when I’m moving 10 MPH or higher or when revving the engine. My drive belts are tight, moderately used, do not have any cracks on them and visually look good.
The noise is loud but intermittent. I know Nissan has the official guidelines to check belt noise. Since this is intermittent, I’m having a hard time re-creating the noise on demand. Any suggestions?

Topic

[Billy]

What year/model/mileage? From that description, could be about anything. A video would obviously, though it’s understood reproducing it on demand is difficult so far. Does it happen more with the AC on?

[ken]

97 Nissan Sentra GXE 111K. Well maintained. Bought it brand new and planning to give it to my kid this summer.
It started happening a few months ago during snow season, so, I haven’t had a chance to turn on the AC since it happened for the first time (it is still cold in here).

[mark lavrack]

I had the same noise on my acura tl. I thought at first it was a belt tensioner, so replaced it. The noise was actually the bearings in the alternator. I drove it until it gave out, replaced it with an oem from the salvage yard and the noise disappeared.

[Billy]

When it’s happening, you can use a section of hose as a stethoscope to localize it. Could be an accessory bearing or engine internals.

[ken]

Thanks for the tips and comments.
I just have to carry a 3 foot long garden hose with me and next time it happens pull over to the side and try to pin-point the source of that noise.
I can’t stop laughing trying to visualize a scenario where a guy has a green garden house shoved in his ear by the side of the road and poking around the engine – straight up comedy. 😆

[ken]

The dreaded high pitch sound came back today when I was buying hamburgers in a drive-through. I was prepared this time with the 3-feet long garden hose. I tried but could not locate the source of the sound. I put one end in my ear and the open end of the hose on the alternator, near the alt belt and body, near the alt pulley, then moved to the compressor area and checked the water pump and PS pulleys but nothing was obvious.
Then I came home and let the car idle. The high pitch sound came back after a few minutes of idling. I tried to diagnose again but failed again, could not locate the sound source.
I did the soapy water test on drive belts and sprayed a lot of soapy water all over the belts while the engine was running. I sprayed under the belts, on and around the pulleys, but it did not get rid of the sound, but after spraying for 3 minutes and half-a-bottle, it changed the tone/pitch of the sound to a lower tone/pitch. But the sound never went away completely. Then the fans kicked in and the engine started revving at higher RPM and the sound went away completely until the fans turned off and a minute later the engine started idling at a lower RPM and at that point the sound came back as I was expecting. Even though I cannot reproduce the sound on-demand, I have narrowed it down to driving short distance and then engine idling for a few minutes. The intermittent high pitch sound comes back when engine revs at lowest RPM regardless the car is moving very slowly or parked or in neutral.
The sound is likely coming from the front of the engine. It goes away when the engine revs at higher RPM or when the fans turn on to cool the engine. When I turn on the air-conditioner, it eventually gets rid of the high pitch sound – I think because the AC makes the engine rev up at higher RPM just like when the fans kick-in.
BTW, even though I only have about 25K on these drive belts, they are 8 years old.
Any idea what may be causing this high pitch sound?

[Mike]

Do you have a single serpentine belt, or a combo of a main serpentine belt and a few V belts going to some accessories?

Do you have a separate V belt going to the power steering pump? That would be the first one I’d look at. See if you can remove that belt and run the engine without it. Keep in mind, it may not be the belt itself, but the pump. You could try the same procedure with the alternator belt, but I personally don’t recommend it. I don’t think it’s a good idea to run a modern computer-controlled engine without the alternator in play; others may disagree. It’s your call.

You could remove all the belts and rotate each pulley by hand, paying attention to physical feel. The pulleys should rotate silky smooth and should have no radial or axial play.

[mark lavrack]

If your belt is eight years old I would start out by replacing the belt(s). Get a good belt. Tighten that belt to specs. While you have that belt off I would spin the compressor to see if you could get any noise. From your description it sounds like its associated with the ac, which it includes the fan motor. Put the belt on and get a stethoscope. Please be careful of moving parts. Place it on the compressor. You have to check all moving parts.

[ken]

Thanks mlavrack and evil-i. I have 2 drive belts. The outer belt runs PS and WP. The inner belt runs ALT and AC. Is there any DIY thing I can do other than buying a stethoscope? I’ll change the belts in a couple of weeks and update.

[mark lavrack]

No problem. I have used this website for a couple years and have learned and fixed my own car. Well pays for having a membership. I don’t know Eric personally, but he sure has a good heart. Fixing it forward is a great program. Just one more word of advice. I pay a membership to Mitchells 1 repair manuals. This is excellent source too. Just a little hard to find information at first, but you will get use to it. Gives step by step repair guidelines. All the professional mechanics use this. One repair savings well pays for both.

[ken]

I am going to replace my drive belts tomorrow. BTW, since my soap water test, the squealing – which was a continuous and loud high pitch sound seems to have have gone away for the most part. I can still hear a very faint squeal when idling for a long time. I hope changing the belts would fix this issue. I’ll update again soon.

[ken]

I was bale to change both belts a few days ago. Now I look back, it was pretty simple to do. As a non-mechanic weekend warrior, I just didn’t know before and was nervous to do it myself.
The new belts are running smooth, no squeal, no dreaded high pitch sound when going through drive through. I’ll update again if the sound comes back.
Thanks to everyone who replied to this thread and to Eric for hosting this.

[Author]

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