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Thread: Leak down test

  1. #1
    Join Date
    Jul 2005
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    Default Leak down test

    To recap the compression test...



    • 1-195
    • 2-192
    • 3-180
    • 4-185
    • 5-190
    • 6-140
    • 7-150
    • 8-192




    Today the results of the leak down test confirm problems with cylinders 6 & 7...



    • 1-90/84 6.6%
    • 2-90/88 2.2%
    • 3-90/86 4.4%
    • 4-90/84 6.6%
    • 5-90/84 6.6%
    • 6-90/48 46.6%
    • 7-90/58 35.5%
    • 8-90/88 2.2%




    I could not determine the source of the leakage in cylinders 6&7 via the leak down apparatus. Hooking up 40 psi shop air to the suspect cylinders indicated leakage to the crankcase.
    JP
    Bigger, Stronger, Faster...

  2. #2
    Join Date
    Jul 2008
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    Default Re: Leak down test

    Shit.. this is in the new motor? Is the short block still under warranty, that's nuts!
    2001 Corvette - Heads, Cam, Intake, Full exhaust, Hotchkiss Swaybars, z06 brake ducts, SS brake pistons & Lines Etc. Lowered & Murdered out.
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  3. #3
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    Default Re: Leak down test

    That is a bummer. Is that mod engine able to be worked on in the mark viii or is the engine coming out?
    I hope it's nothing serious like: broken pistons, extreme cylinder gouging.
    Adam K
    '65 Corvair Corsa new DD
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  4. #4
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    Default Re: Leak down test

    Yes it's the new motor - it will have to come out. I was almost hoping for a "simple" head gasket problem.
    JP
    Bigger, Stronger, Faster...

  5. #5
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    Default Re: Leak down test

    That's a real bummer man, hate to hear it.
    2001 Corvette - Heads, Cam, Intake, Full exhaust, Hotchkiss Swaybars, z06 brake ducts, SS brake pistons & Lines Etc. Lowered & Murdered out.
    2000 Trans AM WS6 - Forged Motor APS Twin Turbo Kit. Full Suspension & C5 brakes.... in pieces currently
    1998 Trans AM STS Turbo
    1997 Jeep Cherokee - when you just gotta go places other things won't take you.
    1995 Mercury Grand Marquis - ugly but comfortable

  6. #6
    Join Date
    Dec 2006
    Location
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    Default Re: Leak down test

    You should be able to tell where it is leaking out to. It should either be bubbling in the coolant, blowing up out of the oil fill with the lid open, blowing out of the intake or exhaust. That way you know what the problem is before teardown.
    repair and detailing, amsoil dealer304-677-5804www.sbfilters.com

  7. #7
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    Default Re: Leak down test

    Nothing was indicated in the adjacent cylinder, intake, exhaust or coolant. But you could definitely tell it was going to the crankcase.
    JP
    Bigger, Stronger, Faster...

  8. #8
    Join Date
    Dec 2006
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    clarksburg
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    Default Re: Leak down test

    You definatly have a rings/piston/bore problem there then.
    repair and detailing, amsoil dealer304-677-5804www.sbfilters.com

  9. #9
    Join Date
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    Buckhannon WV
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    Default Re: Leak down test

    Would need more than 40 psi to get a good idea where it's leaking down at
    1975 Stingray L82
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  10. #10
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    Default Re: Leak down test

    Sorry to hear the news, I hope you get it worked out quickly.

    Sig by RogerStout

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  11. #11
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    Default Re: Leak down test

    Update:

    I purchased a video scope with a small enough head to peek into the cylinders. There were no indications of problems with the bores or the top of the pistons. As a cross-check, I looked inside number 5 and they all looked the same.

    After more diagnostics and some very limited driving, I revisited the compression test.


    Dry test:


    Number 6 - 145 psi
    Number 7 - 195 psi


    Wet test:


    Number 6 - 210 psi
    Number 7 - 230 psi


    I hope that's a good sign.
    JP
    Bigger, Stronger, Faster...

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