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Thread: AC belt related engine bay noise

  1. #1
    Junior Member
    Join Date:  Mar 2019

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    AC belt related engine bay noise

    Figured I'd try the community in case there's some prior experience that can save me some troubleshooting efforts.

    Recently completed a restoration of my Delorean. Key components replaced/repaired relative to this thread -
    1. New AC compressor
    2. New AC belt
    3. New Idler pulley bearings

    I've put on a few hundred miles since that work was completed, and noticed a progessively getting worse noise from the engine bay. https://youtu.be/S1miQHF84JM

    When I remove the AC belt, the sound goes away completely. I figured the belt may have stretched or loosened, so I re-installed and tightened the tension a bit, but still getting a similar noise (not quite as loud as the video).

    Any thoughts? I plan on doing a spray test on the belt tonight, but not really sounded like a belt issue, and I can't imagine having an immediate bearing failure since they were just replaced.

  2. #2
    Administrator Ron's Avatar
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    Double check that the washers/spacers for the bearings are stacked correctly.

  3. #3
    Junior Member
    Join Date:  Mar 2019

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    Yes, all of the washers and spacers are installed exactly per spec. Dont see a wobble in the belt while its running.

  4. #4
    Delorean Guru
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    It is going to be either an idler bearing or the bearing on the compressor. If the noise goes away when the compressor clutch is engaged it is the compressor bearing. You can run without one of the idlers. Switch them one at a time to see if one is noisy. If the belt is tightened too much you damage the bearings. Make sure you have the correct belt and it is not riding on the flat, only the sides and it is running straight. Double check all of the pulleys are lined up and the belt is running straight. Another trick is to spray some water on each and see if the noise changes or goes away.
    David Teitelbaum

  5. #5
    Junior Member
    Join Date:  Mar 2019

    Posts:    12

    Quote Originally Posted by David T View Post
    It is going to be either an idler bearing or the bearing on the compressor. If the noise goes away when the compressor clutch is engaged it is the compressor bearing. You can run without one of the idlers. Switch them one at a time to see if one is noisy. If the belt is tightened too much you damage the bearings. Make sure you have the correct belt and it is not riding on the flat, only the sides and it is running straight. Double check all of the pulleys are lined up and the belt is running straight. Another trick is to spray some water on each and see if the noise changes or goes away.
    Thanks David! Happy to report that I solved the issue last night leveraging the spray bottle test with water. When I sprayed, the noise immediately disappeared. I checked the alignment on the pulleys again, may one more fine tune adjustment (following the instructions of loosening all the requisite bolts), and the noise is now gone. On current belt tension, I've got the spec approximate 1/2 inch deflection currently. So hoping the noise stays away for the foreseeable future.

    Thanks for the help.

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