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Thread: DIY: Homemade Boost Leak Test w/easy MAF replacemet

  1. #1
    Registered User Audi-RS6's Avatar
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    Mech DIY: Homemade Boost Leak Test w/easy MAF replacemet

    Hello everyone,

    Boost leak is MAJOR issue to our cars. It is first step before any mods.

    We have closed circuit system. Air should not be coming out anywhere except exhaust.
    Some one tried to smoke our cars from intake are, but its wrong. Seals are not made to be on pressure and you'll see why.

















    One nut on the right side is under the plastic air ducts. It is 10mm size. Dont loose it...



    Left side nut is easier. Its under the breather hose...





    1 bolt, 2 nuts out and airbox should start moving. Push it upwards and carefully remove it. On the back there are MAF sensor connectors...





    Here are two turbo inlets with MAFs on top...



    Now if you planning to change MAFs, thats how it should be done, no need to open intake box.
    Unplug connectors and remove bolts that hold MAFs from the bottom and its done.





    Back to boost leak: some one smoked the system by closing one MAF and pressurizing another one. Logically its correct, but if you do it this way, you HAVE TO DO IT FROM TURBO INLETS.

    I did my test by closing both MAFs and pressurizing hose that goes to BOV...











    I bought a cap and plastic hose, drilled cap to insert air valve and closed BOV inlet with hose.
    So technically system was closed. And it worked well to find really big air hole.















    You can use car air compressor. Oil cap was closed, because once I opened it, air started to come out. So pressure is traveling through valve covers as-well. I cannot figure HOW TO ADD SMOKE to the test, Maybe someone may suggest easy solution.

    I was able to find a leak below turbo on one of the hoses. But Im sure that's only the beginning...

    Thank you everyone.
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  2. #2
    Registered User snoopra's Avatar
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    Nice write-up! Keeping busy with projects I see
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    Have you re-routed the hoses to the top of the diverter valves? (or was this done for leak test?)
    I don't see the hoses coming off of the t-connector.

  4. #4
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    I closed two turbo inlets and disconnected one hose from Y-pipe to Diverted Valve. Closed DV with hose and clamp (placed cup in case I reach hi psi), and made air valve at another side. Pressurized it and found tons of places it was leaking. Now I'm in process to add smoke to it...

    Quote Originally Posted by melsas View Post
    Have you re-routed the hoses to the top of the diverter valves? (or was this done for leak test?)
    I don't see the hoses coming off of the t-connector.
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  5. #5
    Registered User Brav's Avatar
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    Just made my pressure tester. didn't want to drill, so I used 3 adapters! Say hi, Norman.
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    Registered User kday's Avatar
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    The problem I see with this technique is that you don't really want to pressure test the valve train and piston rings (hence the air hissing from the oil cap above). I guess it's good enough to find gross leaks, but it's not ideal. If the front of the car is in service position, it would be better to block off the throttle body.

    I didn't think to do this on the RS6, but when I was pressure testing the intake on my turbo Miata I unbolted the throttle body from the intake manifold, and inserted a piece of 1/8" thick nylon sheet with bolt holes drilled in it, and then bolted the throttle back on. This sealed up the engine and let me pressure test just the intake system. Something similar could be done with the RS6, but I don't think there is room to loosen the bi-pipe unless the radiator is out of the way.

  7. #7
    Registered User Brav's Avatar
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    Well mine worked very well. there was such a huge leak under the manifold (as I suspected) that i could hear it very loudly. My 2hp compressor couldnt even keep up to keep the system pressurized. Just confirming what I already knew, but .. now I REALLY know.

    How can you eliminate the crank case from a pressure test?
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  8. #8
    Registered User kday's Avatar
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    Hmm, well, actually, I guess in your case this test is better than what I proposed. I was thinking of conventional boost leak testing, where you're focused on the turbo->intercooler->throttle path. Ideally for that you block off the turbos as well.

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    I concur with Kday. With this test, you are pressuring up the valve cover area and also the crankcase, both of which are not designed to see much over atmospheric pressure. If your seals and gaskets are already marginal, this could cause them to blow out and/or leak. At a minimum, I would block the ventilation lines that connect at the turbo inlets, so you are not back pressuring the crankcase ventilation loop.

    -Todd

  10. #10
    Registered User 4everRS's Avatar
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    Would putting cylinder 1 at TDC mean all the valves are closed?
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  11. #11
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    Quote Originally Posted by 4everRS View Post
    Would putting cylinder 1 at TDC mean all the valves are closed?
    No, it doesn't matter what position the crank is in, there will always be an intake valve open or about to open. The concern here is not pressure through the intake manifold, it sees pressure when the motor is running and on boost. My point is that you don't want to pressure up the crankcase and valve cover area.

    -Todd

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