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2001 Infiniti QX4/Nissan Pathfinder - what is this noise? (streamable.com)
submitted 1 month ago* (last edited 1 month 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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[–] 3 points 1 month ago (1 child)

Not sure which noise you're trying to record (it can be hard to capture just right) but I do hear what I think is the power steering pump droning - they all make some noise even when new, as they age they get louder.

A simple test is to turn the steering wheel a little, it should cause the sound to change.

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  • [–] [S] 2 points 1 month ago (1 child)

    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 1 month ago* (last edited 1 month ago) (1 child)

    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 1 month ago* (last edited 1 month ago) (1 child)

    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 1 month ago* (last edited 1 month 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 1 month 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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