Alternator or Idler Pulley?? (or Water Pump?)

Discussion in 'GM Powertrain' started by green4191, Jan 2, 2008.

  1. green4191

    green4191 New Member

    I've got an insanely loud and annoying squeak coming from the general vicinity of my alternator. The noise seems to go away once I hit 3rd gear, or it's just covered up by engine noise. Could this be the bearings going bad in the alternator, or just a simple idler pulley, or what! How can I tell which it is, either way I don't want to end up walking.

  2. ChevyFan

    ChevyFan The Sheriff Staff Member 5+ Years 1000 Posts

    I've had alternators go out and they start to squeak before they go out sometimes. I've also mis-diagnosed a bad idler pulley and replaced it only to have to replace the alternator 2 weeks later. The alternator is a piece of cake to change out. The idler pulley is a big tougher.

    One question, have you changed the belt out in this? It's 68K and the belts only usually last about 60k. My 2002 Trailblazer had the belt start to squeal like a pig over a period of like 2 weeks. I changed the belt and it quieted down again.

    (we need to move this post over to powertrain)
  3. green4191

    green4191 New Member


    No I haven't replaced the belt, however I have inspected it and it looks just fine... What if I were to put some soap or something on the belt to quiet it down for a little bit, that way I could hear if it was something else squeaking other than the belt, would that work? Thanks all , oh, how do I move this to a different forum?
  4. green4191

    green4191 New Member


    thanks for moving it for me!
  5. ChevyFan

    ChevyFan The Sheriff Staff Member 5+ Years 1000 Posts

    I wouldn't use soap. Go to your local auto parts store and look for something called Belt Dressing, it's a small spray can and it usually comes with a strawlike sprayer on it (like WD-40) so you can apply it to the backside of the belt when it's running. I would guess it costs in the $5-$7 range and if it quiets down completely, then you should get a new belt. (You might want to get it replaced anyhow, unless you think it was already replaced)
  6. collinsperformance

    collinsperformance Epic Member 5+ Years 500 Posts

    you might have an alt going out or a bad pulley or both.if you got wd-40 hit the tensioner pulleys and see if the sound goes away if so most likely the pulleys if not alt.
    i just had to replace mine and will poost a writeup soon. it is easy and almost anyone can do it...mike
  7. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    Like Mike posted could be either one but its real easy to isolate the problem so you dont change out good parts.
    A can of WD-40 and and a can belt dressing should cost less than $10 together and may possibly save $75 for the tensioner or $145 for the alternator.
  8. green4191

    green4191 New Member


    Well Saturday morning I got under the hood to discover the true problem... I smelled dex-cool... I started looking and could see where it's been slung left and right and simply dripped straight down from the water pump... Anyways the water pump has already been replaced once and this one was under warranty, so I replaced it again...that fan clutch was fun!!! I'm gonna replace the belt today as I'm pretty sure coolant destroys a belt. Is that really true??? If the noise goes away after the new belt I'll let you know! Thanks All

  9. ChevyFan

    ChevyFan The Sheriff Staff Member 5+ Years 1000 Posts

    What type of water pump did you install that your replacement already went out? Just curious.

    You'll get some noise from a bad water pump. I'm not sure if coolant does anything bad or not, it probably does and a new belt is cheap insurance against being stuck on the side of the road somewhere.
  10. collinsperformance

    collinsperformance Epic Member 5+ Years 500 Posts

    it will make noise sometimes. the coolent coats the belt and it is sticky so it will coat the pulleys and can make noise. it will soak into the belt and soften it and it might fail....mike

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