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Thread: Altenator diagnosis questions, whining noise when warm

  1. #1
    Join Date
    Oct 2017
    Location
    Maine
    Posts
    78

    Altenator diagnosis questions, whining noise when warm

    Ok, to start: 2005 330ci ZHP, 120k miles, 6 spd man

    So here is the story, my car is running great, no dash lights of any kind. When warmed up, I have a subtle whining noise. Gets a little louder with higher rpm, but doesn't really track with rpm. Intake boots are in good shape. The belts and idler pulleys are all new. I can't quite seem to tell where the sound is coming from. One thought was the power steering pump, so I figured a good flush with new fluid plus replace the reservoir because it has a filter and the cap o-ring has failed. No change, still a slight whine when warmed up. I did freshen up the tranny fluid (manual) and diff fluid at 100K with Royal Purple.

    I did some youtube searching and ran across this vid:
    https://www.youtube.com/watch?v=72REiFhvNuE

    I got my voltage meter out to do some testing. My altenator is pushing out about 14.5v and it drops to about 14.2 when lights and accessories are all on. When I switch from DC to check AC as described in the vid, I have 75mV AC. So, I'm not at 50mV, nor am I over 100mV.

    The other oddity is my alternator does not have a cooling shroud on the back and thus no snorkel as I had on my 325 and as shown in real OEM. The PO maintenance records show no evidence the alternator was ever replaced (could be missing record). I neglected to look and see if it was Bosch or Valeo, or something else.

    Thought I would tap into the collective wisdom here:
    Is the information in the vid a valid diagnosis?
    Am I looking in the wrong place?
    Any other thoughts on where this noise may be coming from?

    2005 330ci ZHP

  2. #2
    Join Date
    Oct 2017
    Location
    Maine
    Posts
    78
    Well, my bad. The lower air conditioning belt pulley/tensioner was bad. Replaced it this morning and problem solved.

    2005 330ci ZHP

  3. #3
    Join Date
    Nov 2014
    Location
    Portland, OR
    Posts
    9,607
    Quote Originally Posted by E46Fan View Post
    Well, my bad. The lower air conditioning belt pulley/tensioner was bad. Replaced it this morning and problem solved.
    Been there, man.



    Glad you got it fixed!

  4. #4
    Join Date
    Nov 2017
    Location
    Irvine, CA
    Posts
    429
    Thanks for following up and posting your findings. Glad you got that resolved.

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