Results 1 to 12 of 12

Thread: Does your 330i have a deflection/idler pulley?

  1. #1
    Join Date
    Jul 2007
    Location
    Dublin, Ireland
    Posts
    518
    My Cars
    E39 530i, E91 318i

    Does your 330i have a deflection/idler pulley?

    Hi guys,

    I tried for a response on the E39 forum, but there's considerably more 540i owners than 530i owners, so maybe some of the 330i M54 owners over here might be able to help me!

    I have decided, as preventative maintenance, and hopefully to rectify minor belt squeal in the morning, to replace my belt tensioner and serpentine belt when I do an oil service on the car at the end of December.

    However, I was doing a bit of research and found recommondations to replace the deflection/idler pulley also. This is a small seperate pulley (untensioned) that sits between the water pump pulley and the alternator pulley.

    When I went out to double check my belt arrangement and what pulleys I may need, I realised that I don't actually have a deflection pulley. It just goes straight from the water pump to the alternator.

    I then went and checked the TIS for instructions and there is actually two arrangements; one without the pulley, one with:



    Should I install a deflection pulley? Would there be any benefit in doing so?


  2. #2
    nathancarter is offline Stretch Haters Club #1 BMW CCA Member
    Join Date
    Feb 2007
    Location
    Tampa, FL
    Posts
    11,328
    My Cars
    2002 330i 131k
    My 2002 330i has the deflection pulley bolted to the front of the alternator, as shown in the second diagram. I'm not an expert, but I don't know what benefit there would be to adding one. You might have a different alternator, in which case it wouldn't even bolt on.

  3. #3
    hooRAH is offline Certified Ziptie Mechanic
    Join Date
    Oct 2005
    Location
    West Palm Beach
    Posts
    2,394
    My Cars
    01 330Ci 5spd
    The benefit of a deflection pulley is that you modify the wrap angle on the pullies that transmit torque. The greater the wrap angle, the greater the torque that can be transferred through the pulley. Since the value of torque you're transmitting doesn't change, it translates into longer belt life before the belt begins to slip, assuming the belt doesn't develop cracks and needs to be replaced anyway.
    01 330Ci 5spd / 07 Honda Pilot EX-L
    Will read/reset SRS codes in South Florida for beer money


  4. #4
    nathancarter is offline Stretch Haters Club #1 BMW CCA Member
    Join Date
    Feb 2007
    Location
    Tampa, FL
    Posts
    11,328
    My Cars
    2002 330i 131k
    Makes sense. I can see where that would definitely improve the wrap angle on the alternator pulley. There's barely any belt touching the pulley in the first photo.

  5. #5
    Join Date
    Jul 2007
    Location
    Dublin, Ireland
    Posts
    518
    My Cars
    E39 530i, E91 318i
    Guys, thank you very much for the detailed responses. You've answered everything that I need to know.

    It costs $41 for everthing I need to install the pulley so I'm going to go ahead with it.

    Thanks again!


  6. #6
    Join Date
    Dec 2009
    Location
    N.Ireland
    Posts
    3
    My Cars
    BMW e46 330i
    Hello. While changing my alternator on my 2000 E46 330i I noticed that I dont have a deflection pulley either. I am thinking of adding one but I see that there are two types available, one with the hole off centre, the other with the hole through the centre. (Part numbers 11 28 7 841 228 and 11 28 1 747 130). Which one is the correct one please and where does this bolt to? I have a mechanical tensioner if that makes a difference.
    Am I right in saying that some models were supplied without the deflection pulley, my dealer believes all M54's should have the deflection / idler pulley installed.
    Any help on this matter would be very much appreciated.

  7. #7
    nathancarter is offline Stretch Haters Club #1 BMW CCA Member
    Join Date
    Feb 2007
    Location
    Tampa, FL
    Posts
    11,328
    My Cars
    2002 330i 131k
    Mine is the offset kind.

    For the offset pulley: On the mating surface between the pulley and the alternator, there's a little nub on one side and a dimple on the other side (I don't remember if the dimple is on the pulley, or on the alternator), to hold the pulley in the correct offset postion once it's bolted in. My recommendation would be to look at the front of the alternator, where the pulley goes. If you see the dimple or the nub, get the offset pulley; if you see neither, then get the centered pulley. (note, it may be covered by the bolt head or washer)

    Either one should improve the wrap angle of the belt around the alternator pulley.

  8. #8
    Join Date
    Dec 2009
    Location
    N.Ireland
    Posts
    3
    My Cars
    BMW e46 330i
    Thanks very much, this has been very helpful!

  9. #9
    Join Date
    Jan 2010
    Location
    Auburn, Alabama
    Posts
    17
    My Cars
    2003 330i
    Hi Everyone,
    My wifes 2003 330i has a squeeling noise coming from the drivers side of the engine also. from what I have read on the forum and with the use of a mechanics stethascope I am pretty sure its the idler. I called my local foreign car shop and the parts guy proceeded to tell me he could order it and that the idler was a GM part. Has anyone else heard this?

  10. #10
    nathancarter is offline Stretch Haters Club #1 BMW CCA Member
    Join Date
    Feb 2007
    Location
    Tampa, FL
    Posts
    11,328
    My Cars
    2002 330i 131k
    It's quite possible that the pulley is interchangeable with a GM part, or perhaps even an identical part manufactured by the same third party. Every car has a belt system, after all. My old Mercedes used an alternator that was a GM part.

    If you're having to wait for parts to be ordered, your best bet may be to order it yourself from Pelican, Tischer, RMEuropean, etc. If you're competent enough to diagnose the noise by yourself, you'll have little trouble swapping the pulley - especially if you have a manual transmission with electric fan, which is so easy to remove.

  11. #11
    Join Date
    Sep 2009
    Location
    Pacifica, CA USA
    Posts
    528
    My Cars
    2008 335i, 2001 330i
    Quote Originally Posted by Mez1973 View Post
    Hi Everyone,
    My wifes 2003 330i has a squeeling noise coming from the drivers side of the engine also. from what I have read on the forum and with the use of a mechanics stethascope I am pretty sure its the idler. I called my local foreign car shop and the parts guy proceeded to tell me he could order it and that the idler was a GM part. Has anyone else heard this?
    I agree with Nathan - this is almost too easy to do yourself to warrant paying someone labor PLUS their markup on the part. The part itself can be purchased at Pelican Parts for around $25. The install involves removing the belt, undoing the bolt that holds on the old pulley and swapping your new one in. It's about 30 minutes of labor.

  12. #12
    Join Date
    May 2001
    Location
    Los Angeles
    Posts
    6,106
    My Cars
    e30/36/46 325/M3/330
    my 03/2001 330i has one


    Quote Originally Posted by dallasfan824
    TC does not want ghey hookers you silly.

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •