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  1. #1
    Senior Member Three Rings cincyadam's Avatar
    Join Date
    Jan 16 2011
    AZ Member #
    69559
    Location
    Cincinnati, Ohio USA

    Help Me Diagnose This Noise.. '01 A4 1.8T AWM

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    I'm hearing a "flapping" noise only under heavy load. I thought it was an exhaust leak for the longest time, so I left it until I installed a brand new Borla system from the downpipe back but I'm still hearing it. It's really noticeable when you're driving next to buildings where it can echo.

    Couple of side notes..
    -Car is a 2001 AWM with 157k
    -ALL exhaust gaskets from the test pipe out were replaced with OEM ones
    -Secondary air has been deleted
    -It does NOT make this noise while idling, or in neutral and revving.

    I've ruled out an exhaust leak, since I'm guessing you would hear this noise constantly and not just under heavy load, and the fact that everything is new and I can't find a leak anywhere.

    I've read that this is typically two things, either a vacuum leak (but I've checked everywhere), or it's a intake manifold gasket. (haven't dug into this yet.)

    Any other ideas come to mind? It's driving me nuts now that the weather's nice and I've been driving the A4 daily again. Thanks for any help!

  2. #2
    Active Member Two Rings dmode951's Avatar
    Join Date
    Apr 09 2019
    AZ Member #
    472487
    Location
    CALI

    Check out this thread it might help you.

    Flapping noise at high speeds

  3. #3
    Veteran Member Three Rings HUFset's Avatar
    Join Date
    May 08 2014
    AZ Member #
    214359
    My Garage
    B5 A4 F21L, B6 A4 1.8T, MK4 Jetta F21T
    Location
    CLFX, Denver

    Mine was a boost leak from a one way valve near the intake. Also check your exhaust manifold, turbo to mani connection under a cold start with a bare hand to feel for air escaping before it gets hot in a few seconds.
    2000 A4 1.8TQM|Frankenturbo F21L|550cc Motoza|034 AEM WMI|ClutchMasters FX250|Carbonio CAI|034/Borla TBE|Godspeed FMIC|2.0T/AWP harness|Toy Guy/JHM duo SS|034 mounts|034 CAs|ST Coilovers|A6 strut brace|ECS Rear Diff Mount|Apikol diff bushings|A4 Sport Cloths|Euro S3 FBMFSW|B6 S4 Rearview Mirror|Euro Bolster|S4 interior/exterior|Sport Mirrors|M3 spoiler|Aero Arms|Votex Rack w/Rocky Mounts|A8 Fat Fives|S4 Cluster|P3 VIDI gauge|Pioneer AVH-X4700BS|Alpine PDX-V9|6 Polk DB mids|Eclipse 12"

  4. #4
    Senior Member Three Rings cincyadam's Avatar
    Join Date
    Jan 16 2011
    AZ Member #
    69559
    Location
    Cincinnati, Ohio USA

    Quote Originally Posted by HUFset View Post
    Mine was a boost leak from a one way valve near the intake. Also check your exhaust manifold, turbo to mani connection under a cold start with a bare hand to feel for air escaping before it gets hot in a few seconds.
    Update: there were two loose bolts on the exhaust manifold nearest to the firewall but unfortunately that didn't fix it. The exhaust manifold and turbo-manifold felt fine when I checked this morning.

    Messing around with it more later this evening.



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