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2001 Infiniti QX4/Nissan Pathfinder - what is this noise? (streamable.com)
submitted 4 months ago by to c/mechanicadvice@lemmy.world
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Sounds like gears rubbing or something. Maybe a chain or belt? Sounds like it’s coming from the front of the engine and it goes up and down in pitch with throttle.

For context, I recently got some water in the intake, but not enough to hydrolock. Changed MAF. Idles fine.

Thanks!

EDIT: I think the sound is coming from one of the belt pulleys. Upper left one?

Edit edit: I’m pretty sure it’s the alternator now. Will follow up.

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[–] [S] 1 point 4 months ago (4 children)

Thanks for the confirmation! I think that’s what it is too. Do you think it would need to be replaced or some other maintenance could fix it like flushing the fluid?

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  • [–] 1 point 4 months ago* (last edited 4 months ago) (3 children)

    Probably just age.

    You could try replacing the fluid in the pump itself, that's probably about half the total system volume, but it probably won't make a difference.

    You have checked the fluid level and made sure it's not low, right?

    Something that's pretty telling - if it's noisier on colder days, that's a good sign it's just wear in the pump itself.

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  • [–] [S] 1 point 4 months ago* (last edited 4 months ago) (2 children)

    Thanks! Fluid looks fine. I think it’s actually the alternator. Turning the wheel doesn’t change the sound at all. Sound goes away with belt loose. And I poked a metal rod at different components and the alternator vibrated the most.

    Battery is charging fine though, so alternator is still working. Maybe just a bad bearing?

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  • [–] 1 point 4 months ago* (last edited 4 months ago) (1 child)

    Probably.

    An old shade tree mechanic testing tool is a long screwdriver - press it to a spot on the alternator and rest your head on it just near your ear - it makes a great stethescope.

    If it's the alternator bearing, it'll very slowly get worse, you'll have plenty of time before it fails.

    Honesty I've never seen an alternator bearing fail before the voltage regulator - that's the weakest link. But hey, take what you get, right?

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  • [–] [S] 1 point 4 months ago

    Thanks! I’ll have to get a long screwdriver. I only have a long piece of metal and it does t transmits sound but I can feel the vibrations are stronger on the alternator.

    It’s an old alternator anyways (20+ years, 100k+ miles) so I’ll replace it and hopefully that’ll do the trick.

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