@Zed Head When i wrote that the spinning noise was heard after The motor stop, it s during like 1/2 sec (like a decreasing wizzz) and it s not everytime.

I wonder if you could see the culprit vibrating when it happens. If it's repeatable it might be worthwhile to work the throttle by hand and watch. Probably scary though.

I was checking to restore my alternator but it seems it s more expensive than a new one…

I will go that road I guess…

I checked on rock auto hard to understand the differences between the models and brand?

Do you have an advice ? Terrepower, Rémy, pure energy have no clue about the quality ?

Remy makes new. I have one on my main vehicle, a Ford. Been fine.

I'd still check your damper. Hard to see why the loose alternator pulley/shaft would start vibrating on its own. Seems like something is setting it off. Good luck.

Looks like WAI Global is the only new option though. I think that they make their parts at a variety of places. Surprisingly hard to figure out where. Looks like China is involved, of course.

https://en.abrams.wiki/Wai-Global-Div-Of-Wetherill-AssociatesInc/3--ddg-f2fixlRbpNOdw1wjQ

https://en.abrams.wiki/tools/companytransparency/dashboard/3--ddg-f2fixlRbpNOdw1wjQ/suppliers

https://www.rockauto.com/en/catalog/nissan,1978,280z,2.8l+l6,1209260,electrical,alternator+/+generator,2412

Just a thought, Not trying to wear the black hat by any means. When you removed the belt it took 4 variables out of play. Alt. Water pump and fan clutch, and the harmonic balancer. My suggestion would be to remove the alternator, take it to a parts store where they offer free testing. Chances are the alt. Is good, but does it make that same noise during testing. If so you found your culprit and feel more comfortable moving forward purchasing an alternator. My two cents on diagnostics. Doesn’t cost you anything for peace of mind. You’re removing it anyway.

Hi Yarb

I Will test it with an electric drill to reproduce the sound if I can… Will see

I Will update the post

Hi Zed Thanks for the references and the info

Where are you located? Tension on the belt is key to create bearing noise. Do you have a parts house where they test alternators?

Some update

I finally had the time to change the alternator and no change

I am quite disapointed I must say

Same f### noise

I have no culé Except start a fire with the Z

Read back over the thread and try the other suggestions. Water pump, fan, fan clutch, damper pulley, etc. Watch the pulleys and belts while the noise is happening. Light things up with a bright light.

That one belt has 3 other variables. Shotgun technique is an expensive way to troubleshoot. @Zed Head had a good point look back in the thread.

Hi

I changed the fan clutch and no change :-(

My water pump seems quite new…(see photo)

I am hesitating to change it. What do you think ?

I Check the damper pulley and it looks good

Take a piece of tubing, 2 feet.. put one end to your ear, and look for the noise with the other end, watch out for the fan! But i bet you will find the bearing or so that makes the noise within minutes!

Very interesting noise, let us know what it was!🙂