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  • 2 Post By firebird77clone

Thread: Thunking Noise after Turning the Car off

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  1. #1
    nathantaylor200 is offline CHR Junior sMember Visit my Photo Gallery
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    Apr 2016

    Thunking Noise after Turning the Car off


    Disclosure: I am new to car mechanics so please be patient with me.

    What I have:
    I have a 1965 Impala and just rebuilt a '74 350 for it(cast-iron), please spare the criticism for not sticking with the 283. The new 350 also has vortec heads and I also installed a flex fan.

    The Issue:
    About a third of the time when I turn the car off I hear this thunking noise that really sounds like the flex fan is hitting something because it slows down like, "thunk..thunk....thunk........thunk" but the engine definitely stops right when i turn the ignition off so it is not a run on or anything. I have also verified that the fan is for sure not hitting anything even though that is how I described the sound I am pretty sure that is not it. I did find this forum, Pressure in motor - knocks when I shut it off
    that mentions a possible pressure release happening but no resolution was posted. Overall the engine runs great, a little bit of an oil burner but nothing to complain about. Any help is appreciated.

  2. #2
    34_40's Avatar
    34_40 is offline CHR Member Visit my Photo Gallery
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    Sep 2007
    New Bedford
    Car Year, Make, Model: 34 Ford 3W Coupe Replica

    Welcome Aboard, Nice to see you here.
    Have you done any checks yet? I'd be checking things like the flywheel / flexplate, torque converter fasteners ( if auto trans car) or perhaps pull a fan belt off and isolate the alternator or power steering pump (if equipped) or water pump??

  3. #3
    36 sedan's Avatar
    36 sedan is offline CHR Member Visit my Photo Gallery
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    Apr 2012
    american canyon
    Car Year, Make, Model: 36 Ford Sedan, 23 T Bucket

    I had a vacuum brake booster with a bad check valve that made some crazy noises when it was shut off, lasted about 30 seconds or so (if memory serves)?

  4. #4
    firebird77clone's Avatar
    firebird77clone is offline CHR Member Visit my Photo Gallery
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    Sep 2005
    Car Year, Make, Model: 69 nomad, 73 charger, 74 vega

    Sounds like you have taken some flak for upgrading the engine.

    Don't let it bother you, it's a good upgrade.

    You might try having someone shut down the motor while you are under the hood listening.
    ted dehaan and Rrumbler like this.
    Education is expensive. Keep that in mind, and you'll never be terribly upset when a project goes awry.

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