Thank you for the advice. The last time I had a compression tester, both
vehicles in the driveway had carbuerated slant-six engines.

John

On Fri, 2011-12-23 at 01:48 -0600, John Rodgers wrote:
> Mike that is a pretty good summation of the procedure. I still have my
> old aircraft engine compression tester from my aviation days. Works.
> Tells me what I want to know, exactly as you have described it. And you
> are very correct to advise being very careful of kickover when the
> engine is under that much pressure at TDC. It can break an arm, or
> worse. Imagine a 6-8-10-12 foot propeller suddenly kicking over during a
> compression test using the TDC method. Disaster -  is how the newspaper
> reported the incident  the lady at the airport backed into a turning
> propeller. Even a single blade kicking over from TDC can ruin your day -
> and so  can an auto engine.
>
> John
>
> John Rodgers
> Clayartist and Moldmaker
> 88'GL VW Bus Driver
> Chelsea, AL
> Http://www.moldhaus.com
>
>
> On 12/22/2011 10:01 PM, Mike wrote:
> > Not sure which ones are better than others, but I'm not sure if you
> > understand the use of these diagnostic tools.
> >  A compression tester and a cylinder leak-down tester check different
> > things in different ways, so you should use both.
> > You could get a compression tester on loan from Autozone or Advanced Auto
> > Parts, and test for general overall compression readings.  This is
> > done by
> > turning it over with the starter, with all the sparkplugs removed.
> > You want
> > to see no more than a 10 percent total difference from the highest
> > cylinder
> > reading to the lowest one.  For example, if the highest cylinder read 130
> > psi, then 10 percent (13 psi) subtracted from that would be the lowest
> > acceptable reading from any other cylinder, which equals 117 psi minimum.
> > All four cylinders should be in that range from highest to lowest, or
> > there's too much imbalance between cylinders compression.  This would
> > indicate that something needs attention.
> >  Here's where a leak-down tester is the next step in engine
> > diagnosis.  You
> > turn each cylinder to TDC and hold it there with a socket and breaker
> > bar,
> > then add 80 psi of compressed air on the first gauge of the leak-down
> > regulator.  (be careful, that cylinder can turn fast and hard enough to
> > break your wrist!)  The second gauge will read the pressure that that
> > cylinder is leaking-down.  If it's a little, it's okay.  If it's
> > leaking a
> > lot, something is wrong.  You can hear the air pressure that's leaking
> > coming from somewhere in that cylinder.  If you hear it at the intake,
> > then
> > it's leaking from the intake valve; if you hear it at the tailpipe, it's
> > leaking from the exhaust valve; if you hear it leaking from the oil
> > filler,
> > it's leaking past the rings.  This test is really only needed if the
> > compression test is very low, or extremely uneven across the 4 cylinders.
> > If the engine runs well, smooth and powerful, your compression will
> > probably
> > check high and even.  100 to 160 psi is fine, and is dictated by the
> > compression ratio of the engine, so it obviously differs from one
> > engine to
> > another.
> >
> > Hope this helps,
> > Mike B.
> >
> > -----Original Message-----
> > From: John Lauterbach
> > Sent: Thursday, December 22, 2011 10:08 PM
> > To: vanagon@GERRY.VANAGON.COM
> > Subject: selecting a compression tester
> >
> > One of the few advantages of the recent problems with my '84 Vanagon is
> > that my Son, age 13, has taken a sudden interest in the Vanagon and
> > wants to get his hands dirty testing it and fixing it.
> >
> > Several list members have mentioned need for a compression test and a
> > leak-down test.  Local shops are already on Christmas schedule
> > (remember, this is the Deep South), so any testing will be DIY and a
> > chance to further my Son's practical education.
> >
> > Are any of the compression testers at the stores still open any better
> > than others?  Local AutoZone has a tester for $40 that included the
> > screw in adapters for doing the leak-down test (already have air
> > compressor).  I have the usual array of stores available to me.
> >
> > Thank you in advance.
> >
> > John
> >
> >
> > -----
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> >