What's causing this noise?

[Veleno]

So I started the car after doing some maintenance that I hoped fixed a noise I heard when I purchased the car. Turns out the noise is still there. With the airbox removed I can hear it more, and it sounds like it's coming from the alternator or the alt. pulley. Has anyone heard this noise before or can point me in the right direction to look/check? After the car warms up for about 10-15 minutes, it appears the noise goes away or only happens once in while for a short time.

Video won't attach, so here's the link:

https://youtu.be/kx1GL3ZTTCU

Thanks in advance for the help.

[AJLM34A]

It is either a bearing in the alternator or in an idler or tensioner.

Using a stethoscope or a long thin screwdriver as a stethoscope, you can try to isolate which one or more of them is making the noise.

[importbanana]

remove belt, start car, noise gone? Something driven by the belt or belt itself is the cause. Turn all wheels by hand to see if one feels bad. Only run car max. 20 seconds when belt removed, because water pump doesn't run without belt.

[Veleno]

It is either a bearing in the alternator or in an idler or tensioner.

Using a stethoscope or a long thin screwdriver as a stethoscope, you can try to isolate which one or more of them is making the noise.

Yeah I was thinking of using a stethescope, just have to get one or borrow one.


remove belt, start car, noise gone? Something driven by the belt or belt itself is the cause. Turn all wheels by hand to see if one feels bad. Only run car max. 20 seconds when belt removed, because water pump doesn't run without belt.

I should have turned the pulleys when I had both belts off (replaced both belts and the idler pulley).

[Braymond141]

For starters you have the belt on wrong. The belt goes under the idler pulley, not over.

The issue could be the belt drive or the alternator. You'll need to inspect more.

[Veleno]

For starters you have the belt on wrong. The belt goes under the idler pulley, not over.

The issue could be the belt drive or the alternator. You'll need to inspect more.

Thanks for catching that Brett. It didn't look right to me but thought that's the way it's supposed to be based on this video I watched. Lesson learned!
https://www.youtube.com/watch?v=81HAc-mqrHE&ab_channel=AutoWerksofAmerica

I'll try to identify the culprit this weekend!

Thanks guys!

[mmark.]

That is the dry ball bearings in an idler pulley.

[Veleno]

That is the dry ball bearings in an idler pulley.

The idler pulley is new, I replaced it with another ina pulley. Maybe the tensioner pulley (real oem calls it "adjusting pulley")? I spun it around and it spins freely. My old idler pulley also spun freely which indicated it needed to be replaced.

[RBNetEngr]

They should spin easily, but not like a pulley bearing with zero friction. If that’s what you have, then the bearing is probably worn, and causing the noise when under pressure from the belt tension.

I had one pulley (don’t remember which one it was right now) that was totally silent, and then just seized and broke apart. I was pulling into a parking lot, and suddenly the charging lights came on the instrument panel, and steering got real heavy, so I knew the belt came off. Fortunately it didn’t break my fan, but the belt did get wrapped around the crank pulley and was damaged beyond usefulness.

-rb