Date: Thu, 27 Jan 2005 13:16:29 -0500
Reply-To: Don in North Carolina <Don_Dixon@BELLSOUTH.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Don in North Carolina <Don_Dixon@BELLSOUTH.NET>
Subject: Re: How does a leak down tester work???
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reply-type=original
Ok, how about if a different Don takes a stab at it?
Most leak down testers have two gauges, one showing the regulated pressure
being supplied, and one showing the pressure in the cylinder. Assuming a
100 PSI regulated supply, and as an example a reading on the cylinder
pressure gauge of 90 PSI, you would say that the leak down on that cylinder
is 10%. A good leak down on a race engine is in the 3-5% range. A regular
motorcycle engine will also read in this range. A car engine can be in the
10-15% range, but the lower the better.
A leak down tester is a good tool, but it should not be used as the only
test to determine the state of an engine. Regular testing using both a
compression tester and a leak down tester will show the overall health of an
engine in a much clearer light. On my motorcycles, I have a compression and
leak down test done about every 10K miles, depending on the age of the bike
and how it is being used (or abused!).
Assuming that both leak down testers have both of their gauges calibrated,
and assuming that the tests were done correctly (TDC of power stroke, etc.)
then yes, the numbers can be compared to one another.
Don in Reidsville, NC
1987 Vanagon GL Syncro (Suzie)
1988 Vanagon GL (Sylvia)
----- Original Message -----
From: "tabe johnson" <xtabe@YAHOO.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Thu 27 January 2005 12:22
Subject: Re: How does a leak down tester work???
> Hi Don,
>
> Thank you for the detailed procedure.
>
> I must not be making myself very clear, because both the
> responses to my question I have read have given me a
> detailed description of the process of doing a leak down
> test. Here are questions:
>
>
> Where does the % leakdown number come from? Can the number
> be compared between different testers and engines?
>
> Think about these questions for a minute and you'll see it's
> not totally simple.
>
> Thanks!
>
> --tabe
>
>
>
>
> Date: Wed, 26 Jan 2005 12:11:20 EST
> From: Don Deitke <DVWImports@AOL.COM>
> Subject: Re: How does a leak down tester work???
>
> The air test or leak down test is used to determine any wear problems
> within
> any given engine . I will explain the test very simpily to all . // You
> want
> to bring your piston to top dead center of each cylinder to be tested or
> actually the firing position NOT to the bottom center. // You will first
> remove all
> 4 sparkplugs from your engine,also your oilcap, and if watercooled your
> radiator fill cap // You will need a air compressor with a adjustable air
> regulator
> plus a air test hose that may be purchased at your local parts stores and
> it
> will have a end to thread into the sparkplug hole and a male quick release
> end to connect to your air hose. To run the test properly run and get the
> engine to operating temperature before removing plugs. // Your FIRING
> ORDER is
> 1-4-3-2 ~~ You have a V notch on your crank shaft pulley and that notch
> will
> show up on Number 1 cylinder and Number 3 cylinder. // You will need to
> find
> number 1 plug wire on your dist.cap and that will lead to the drivers side
> towards the front of the van number 2 is on the drivers towards the back
> of the van
> Number 3 is on the pass.side towards the front of the van and Number 4 is
> towards the back of the van // if you have standard shift place van in
> neutral
> and ebrake IT // Remove your distributor cap and turn the V notch to the
> coresponding top dead center marks ~~refer to your Bently manual ~~ You
> can
> usually turn the engine on the alternator center nut ~ Turn engine
> Clockwise //
> Once you find Number 1 TDC // Insert your test hose into number 1
> cylinder
> then connect your air hose to the test hose with 0 air pressure at the air
> regulator,slowly turn air up to 75 to 100lbs. Now if you have a problem in
> the test
> cylinder the air will tell the tale // to go to next cylinder to be
> tested
> turn clock wise 90 degrees and make sure your rotor points to the correct
> wire
> on your dist cap // If a exhaust valve is leaking you will have air coming
> out
> the end of the muffler .// I f the intake valve is bad you will have air
> coming out the air intake or on carbed out the carb.// If you have
> piston ,ring
> or cylinder wear problems the air will blow past the rings and into the
> oil
> area and you will be able to hear it at the oil fill region // If your
> head
> gaskets are bad you will see air bubbles or antifreeze coming out the
> radiator
> fill cap .On horizontally opposed engines always replace the
> piston,cylinder and
> rings as a kit never replace just rings, you will be putting new round
> rings
> into 2 egg shaped objects = piston & cylinder NOW ??? The reason for
> having
> the piston at top dead center is to test the area at the top of the
> cylinder
> and the rings for proper combustion which is the area IN which your power
> and
> compression originates from == Combustion ) ALL these tests can be done
> on 4
> / 6 / 8 cylinder engines.// You can have problems in all areas so listen
> in
> all area,s to be sure . You should also run a a compression test first to
> decipher any pre air test problems !!! Average good compression tis 150
> to 170 lbs
>
> We do not list parts on our Online Catalog for the early Air & Watercooled
> Van, Vanagon or Bug ~~ But we do have a complete parts supply for the
> early
> models / Just email or call in your Requests // For reference please
> print the
> test procedures and have it right on your test site !!! Any questions
> just
> email
>
> Thanks to ALL Don @ DVW Online Catalog
> www.dvwimportautoparts.com
> Ph. 814-266-9335
>
>
> ______________________________________________________________________
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