Leak Down test and oil use...again

Bernie Benz b.benz at charter.net
Wed May 19 09:21:14 EDT 2004

Thanks John,

So there must be a flow restricting orifice between the regulated supply
pressure and the measured cylinder pressure, across which the leakage causes
the pressure drop.  Is this a "standardized" test procedure, i.e. results
comparable between different test devices?

If not careful, one can learn something every day!


> From: "John Gourley" <azaudi at MSN.com>
> Date: Tue, 18 May 2004 22:24:04 -0700
> To: "Audi 200Q 20V" <200q20v at audifans.com>
> Subject: Re: Leak Down test and oil use...again
>> Derek,
>> I still don't understand your explanation of the percentage figures for
>> your
>> leak down test because I don't understand what test flow restriction is in
>> between the measured input and output pressures,
>> Bernie
> If i may step in this discussion........with the leakdown tester you connect
> the air hose from the compressor to the tester....adjust the gauge on the
> tester to 100 psi of air...make the connection to the cylinder you are
> testing....whatever the number Derek mentioned, let's say 20%.
> All it is, that cylinder is leaking 20% of the air pressure going into that
> cylinder, therefore 20% leakdown on the cylinder.  So it really isn't a
> complicated tester, simply measuring what percent of the air pressure going
> into the cylinder leaks out.
> Using a leakdown of course take more time than a compression test but as
> Derek pointed out, the nice thing about a leakdown it helps point you closer
> to the problem area...listening for where the air pressure is
> leaking.........air pressure from the tailpipe, exhaust valve........air at
> the intake, intake valve.......bubbles in the engine coolant, head
> gasket...etc
> John Gourley 
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