AC Belt Sound - Nissan : Datsun ZCar forum :Nissan Z Forum: 240Z to 370Z
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post #1 of 8 (permalink) Old 12-04-2018, 11:59 AM Thread Starter
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AC Belt Sound

Hi guys,

My AC belt has always made this swishing noise (tried 2 different belts & had the compressor rebuilt), could this be the pulley?

If i spray silicone lubricant on the top of the belt (while it's running), the swishing noise goes away temporarily.

Do all belts make this noise or is my pulley dying? Many threads I've read say that the pulley makes a squeal noise when its dying which isn't the case here.

Here is a video of the sound: https://youtu.be/arjpSrqKiHA


Any ideas?


-chase

1978 280z - stock L28 engine - Dallas, TX

Last edited by chaseincats; 12-04-2018 at 12:01 PM.
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post #2 of 8 (permalink) Old 12-04-2018, 03:57 PM
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Pinpointing the exact location of an under-hood noise can be notoriously difficult. Fortunately, you're dealing with a single belt that drives a single accessory.

So let's begin with the premise that, no, all belts do not make the noise depicted in the video.

To the naked eye, and understanding that we're seeing only a brief video clip, there doesn't appear to be an inordinate level of run-out on the compressor pulley, so it's probably not that. So if the compressor's been rebuilt, and if you've tried multiple belts and if the noise disappears when using a lubricant, it seems a reasonable assumption that your problem lies elsewhere.

Assuming your car is similar to mine, there should be an adjustment bolt/idler pulley just above your A/C compressor. Wild guess (well, not that wild I guess, as there's not too many things it could be), but I'd look at it as the culprit.


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post #3 of 8 (permalink) Old 12-04-2018, 04:56 PM Thread Starter
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Originally Posted by nkowi View Post
Pinpointing the exact location of an under-hood noise can be notoriously difficult. Fortunately, you're dealing with a single belt that drives a single accessory.

So let's begin with the premise that, no, all belts do not make the noise depicted in the video.

To the naked eye, and understanding that we're seeing only a brief video clip, there doesn't appear to be an inordinate level of run-out on the compressor pulley, so it's probably not that. So if the compressor's been rebuilt, and if you've tried multiple belts and if the noise disappears when using a lubricant, it seems a reasonable assumption that your problem lies elsewhere.

Assuming your car is similar to mine, there should be an adjustment bolt/idler pulley just above your A/C compressor. Wild guess (well, not that wild I guess, as there's not too many things it could be), but I'd look at it as the culprit.


_
Sounds good, ya that was the pulley I was thinking but was thrown off when everyone was saying that if that pulley is dying it makes a screeching sound

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post #4 of 8 (permalink) Old 12-05-2018, 02:40 AM
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Is there a flat idler on there? It could be the belt screeching on it.
Silicone makes things slippery. There are belt dressings that make the belt "stickier", if applied sparingly. If sprayed it will get sticky on other things, too.

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post #5 of 8 (permalink) Old 12-05-2018, 10:46 AM Thread Starter
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Is there a flat idler on there? It could be the belt screeching on it.
Silicone makes things slippery. There are belt dressings that make the belt "stickier", if applied sparingly. If sprayed it will get sticky on other things, too.
I'm not sure what a flat idler is but the pulley we're talking about is on top:

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post #6 of 8 (permalink) Old 12-05-2018, 07:54 PM
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Nope, that's sure not flat. But it could be the squealer if the bearing is going---although you say spraying the belt itself cures the sound.
Is the belt the right size? A small increment in belt size could be taking the idler to it's maximum movement and not totally gripping the belt. Or if the belt is old and "hard" and slicking on the sides. Or if the belt is narrower in width but the same listed length it will ride deeper in the pulleys, essentially making the idler travel further to try to take it up. my .02c

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post #7 of 8 (permalink) Old 12-07-2018, 02:25 AM Thread Starter
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Thanks for all your help guys, changing the idle pulley bearing fixed the sound!

1978 280z - stock L28 engine - Dallas, TX
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post #8 of 8 (permalink) Old 12-09-2018, 02:12 PM
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You can also treat the belt by holding bar soap up to the underside of the running belt. That will only work for a while. But to fix it long term, remove the pulley, disassemble, grease bearing (May have to remove the side seal to pack it), and paint the pulley. The belt running on the shiny metal is what causes the squeaking.

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