Date: Sun, 2 Jun 2013 08:33:13 -0500
Reply-To: raceingcajun <raceingcajun@COMMUNICOMM.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: raceingcajun <raceingcajun@COMMUNICOMM.COM>
Subject: Re: Compression test - cold engine or warm engine? PLUS USED CAR
BUYERS TIP!
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While Dennis is right about compression should be checked on a "warm"
engine. I would add, that the engine should not be at "running"
temperature! I was in a hurry and did this once on an engine I had just
pulled in from a road test, I knew which cylinder was missing, so I pulled
that plug and ran the test on that hole only. When I ran the test, The
compression "air" was so hot it burned/melted the seals in my tester. On
this peculiar tester in was only a "shradder valve", and cheap and easy to
replace. But on some high dollar testers it might be a more expensive
proposition. I might add another point, when doing the test, you want a
fully charged battery, you should pull all the plugs, plus block the
throttle opened! One more thing, you should disconnect the power (+) to the
coil. Coils be mean and will bite!
Don't forget what my Daddy called the used car buyers, "side of the road
compression test". When road checking a used car for a potential purchase ,
and you suspect might have a burnt valve or what ever. Stop in a safe place,
pull the coil wire, crank the engine over. Notice the sound it makes. When a
cranking engine comes to a cylinder with low or no compression, the sound it
makes wont be even, it will "Skip" and speed up slightly at the cylinder in
question. This makes a very noticeable sound as the starter load changes, it
speeds up and slows down at the low drag cylinder. While this wont tell you
which hole is bad, it will wave a flag, letting you know further tests are
required, and should help push the price down and save $$$$$$ !
We also have the wet or dry compression test, along with the leak down
test. All these tricks/tests are great engine condition information givers,
and should be in your arsenal of tools, mental and otherwise!.
Ah the world of automobile LUV! OK........... RAINY SUNDAY MORNING,
TIME FOR A KNAP!
Howard
>Subject: Re: Compression test - cold engine or warm engine?
> Engine should be warm. You want the oil splashed around so the rings can
> seal. For the best diagnostics you also want to do a leak down test. The
> two
> results together can give you a lot more information.
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