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Thread: Can you identify this sound? Possible Alt or pulley bearings?

  1. #1
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    Can you identify this noise? Possible Alt or pulley bearings?

    The car in question is a 2000 323ci convertible with a manual transmission and approximately 112k miles.

    This sound seems to be coming from the area of the alternator and is RPM and not speed dependent. However it sounds nothing like the videos I've watched for either failing alternator or idler pulley bearings. It often goes away after a few mins of driving at higher speeds. FYI- from approximately the :20 to :30 marks, I'd turned the AC on and off a few times to rule out the AC compressor.

    So, any thoughts???

    Last edited by VCOUI; 04-26-2017 at 08:26 PM.
    "Sometimes, it's all about the journey..." Current Bimmer: 2000 323ci Convertible

    Past Bimmers: 2006 Z4 3.0si, 1997 528i, 1995 M3, 1989 325ic, 1973 2002 tii, 1987 528e, 1982 528e

  2. #2
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    Take the belt off and feel pulleys for any play. It almost sounds like a fan that is wobbling and rubbing on something.

  3. #3
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    So update. I took the airbox off to get a better idea. Using the automotive stethoscope, I definitely sounds like it's coming from the *back* of the hydraulic belt tensioner, toward the motor, which seems odd. I wouldn't think the tensioner would make noise, only the tensioner pulley. Any thoughts? Is there something behind the tensioner that could make noise? Also, FWIW, it appears the tensinoer is much newer the the other parts around it.
    "Sometimes, it's all about the journey..." Current Bimmer: 2000 323ci Convertible

    Past Bimmers: 2006 Z4 3.0si, 1997 528i, 1995 M3, 1989 325ic, 1973 2002 tii, 1987 528e, 1982 528e

  4. #4
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    Belt tensioner?

  5. #5
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    Yes, mechanical tensioners do start making funny noises on these - it's a known fact.

  6. #6
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    It's your water pump. Change it asap. Mine did the same thing and the water pump snapped horizontally and the fan clutch blade hit the radiator and the end result, catastrophe. Had to replace radiator, tensioner pulley, clutch fan blade.
    Fun fun fun...

  7. #7
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    Quote Originally Posted by Mless5 View Post
    Take the belt off and feel pulleys for any play. It almost sounds like a fan that is wobbling and rubbing on something.
    Quote Originally Posted by drewusmaximus View Post
    It's your water pump. Change it asap. Mine did the same thing and the water pump snapped horizontally and the fan clutch blade hit the radiator and the end result, catastrophe. Had to replace radiator, tensioner pulley, clutch fan blade.
    Fun fun fun...
    Remove belt, start engine, listen carefully for sound type and location. A few seconds won't hurt it.
    Turn off engine, then before you reinstall belt-attempt to spin and wiggle each pulley by hand.
    The pulley/bearing that wiggles or grinds, makes a noise is the culprit.

  8. #8
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    Remove belt from water pump and see if you can wiggle the pump. If you can, change the pump ASAP.

  9. #9
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    UPDATE:
    So I removed the belts and sure enough, the hydraulic tensioner pulley is giving up the ghost. Thank goodness! I'm just grateful it wasn't the water pump or timing chain tensioner... Is it safe to drive like this until I can replace the pulley or do I risk it seizing up and killing the belt and worse?

    ...Video to follow.
    "Sometimes, it's all about the journey..." Current Bimmer: 2000 323ci Convertible

    Past Bimmers: 2006 Z4 3.0si, 1997 528i, 1995 M3, 1989 325ic, 1973 2002 tii, 1987 528e, 1982 528e

  10. #10
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    I would not drive it, due to the risk of catastrophic failure!
    Order the part from FCPEuro, drive a rental if you must.

  11. #11
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    Got it... do not drive!

    So here's the video, and I forgot about one other matter until I watched it... What about water pump pulley? Take a look and tell me if that's of any concern... I had to rock the pulley from back to front to make that noise.

    Last edited by VCOUI; 05-01-2017 at 08:10 PM.
    "Sometimes, it's all about the journey..." Current Bimmer: 2000 323ci Convertible

    Past Bimmers: 2006 Z4 3.0si, 1997 528i, 1995 M3, 1989 325ic, 1973 2002 tii, 1987 528e, 1982 528e

  12. #12
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    Most likely the bearing on the pump is going bad. Just replace the pump and sleep tight for a few years. Pat yourself on the back for preventing 2 really big accidents.

  13. #13
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    I'd change the water pump and ALL of the pulleys and the idler. When you had the belt off, did you check all of the pulleys (idler)? If they were really easy to spin, like you could flick one and it just kept spinning, it's going bad. There's just too much bad stuff that can happen if a pulley fails. Not worth the risk. If the water pump lets go, odds are that changing the water pump will become the least of your worries.

  14. #14
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    The idler pulley was snug, but not tight. It would turn freely, and smoothly, but as soon as I'd let go, it'd stop. Is that good or bad? I'll probably replace it anyway while I'm at it, but I'm just curious for future reference.
    "Sometimes, it's all about the journey..." Current Bimmer: 2000 323ci Convertible

    Past Bimmers: 2006 Z4 3.0si, 1997 528i, 1995 M3, 1989 325ic, 1973 2002 tii, 1987 528e, 1982 528e

  15. #15
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    A good pulley should turn smoothly and freely, but should not continue to spin when you flick it. Snug is good. I just tend to replace all of those sorts of parts at once. Assuming that they are all of similar age, when one goes, odds are that the others aren't far behind. Of course, take what I say with a grain of salt. I'm just a bit paranoid when it comes to water pumps and pulleys. I had a water pump let go when I was a teenager and I could believe how much damage that thing did.

    Honestly, with your car having 112K miles on it, it's due for a cooling system revamp, if you haven't done it. I'm new to BMWs myself, so I'm assuming that your E46 is similar to mine ('01 325i) in terms of setup. If it is, and your cooling system hasn't been refreshed, I'd say that you're on borrowed time. I'd spend the $500 or so and remove all doubt. Radiator, expansion tank, all pulleys, water pump, thermostat, hoses. It really doesn't take very long to do it and it will give you peace of mind. I bought my E46 with 75k miles on it and the first thing I did was a cooling system refresh. The bad stuff that can happen if any part of the cooling system fails is down right scary.

  16. #16
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    Quote Originally Posted by TonyAngel View Post
    A good pulley should turn smoothly and freely, but should not continue to spin when you flick it. Snug is good. I just tend to replace all of those sorts of parts at once. Assuming that they are all of similar age, when one goes, odds are that the others aren't far behind. Of course, take what I say with a grain of salt. I'm just a bit paranoid when it comes to water pumps and pulleys. I had a water pump let go when I was a teenager and I could believe how much damage that thing did.

    Honestly, with your car having 112K miles on it, it's due for a cooling system revamp, if you haven't done it. I'm new to BMWs myself, so I'm assuming that your E46 is similar to mine ('01 325i) in terms of setup. If it is, and your cooling system hasn't been refreshed, I'd say that you're on borrowed time. I'd spend the $500 or so and remove all doubt. Radiator, expansion tank, all pulleys, water pump, thermostat, hoses. It really doesn't take very long to do it and it will give you peace of mind. I bought my E46 with 75k miles on it and the first thing I did was a cooling system refresh. The bad stuff that can happen if any part of the cooling system fails is down right scary.
    TonyAngel is absolutely correct. I've purchased two E46s in the last year and within 60 days of purchase, I zero-timed the cooling systems on both of them. I'd add that replacing the two plastic water pipes under the intake manifold is paramount - I've worked on a number of these engines and every one of them had pipes that were starting to rot out where they connect to the engine. It's a fairly involved job - the best way is to remove the intake manifold to get access - but if you're careful and methodical, and replace all the fiddly plastic bits in there while you're at it, you've just bullet-proofed your car for another ten years.

  17. #17
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    Preventive maintenance is so crucial on a BMW, that a cooling system refresh is a common maintenance procedure.
    Any used BMW, over 5yrs old-50,000mi is scheduled for a cooling system refresh.
    I mean a complete refresh, not just a hose and waterpump, or thermostat and hose.
    When we say complete cooling system refresh is needed, we mean complete.
    This is a preferred example:https://www.fcpeuro.com/products/bmw...t-mangocoolkit

    This is not meant to imply that BMW is not as reliable or more prone to repairs,
    But to emphasize that repairs cannot be done piecemeal, at least not if you require reliability.
    Preventive maintenance prevents post failure repairs, which are much, much, more costly.
    Just trying to reaffirm and pass-on the truths I've learned concerning BMW maintenance and repairs,
    as compared to other common car manufacturers, such as GM or Honda, Nissan.

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