Did you do the test with a warm engine and throttle wide open? You results
may change.
Yes, if the reading came up with the additon of a squirt of oil, then the
oil is most likely aiding in ring seal...but again, this must be done to a
warm engine (throtte at wide open...to be considered accurate.
What you describe below is not an actual leak-down test, but can (assuming
you can hear the leaks) aid id diagnosing your engine. An actual leak down
test is done with two gauges btween an small orifice, pressure is put into
the cylinder (via compressed air) with both valves closed, then the rate of
leakage is monitored on the gauge.
> [Original Message]
> From: Dana Muise <dana@spazzco.com>
> To: <oletrucks@autox.team.net>
> Date: 1/23/02 11:12:24 AM
> Subject: [oletrucks] leak-down compression test
>
> Hey truckers
> I did a compression check on my old 235 last week and all 6 cylinders
came in
> about 10 lbs below the minimum. The manual said to put a little oil into
the
> cylinders and try it again. They all checked great after that. People are
> telling me this indicated worn rings. Does any one have any theory on
this?
>
> I'm going to perform a leak-down check this week-end. I'm told you have to
> listen at the tail pipe or intake for hissing (bad valves) or oil
breather for
> bad rings. Is this right? It doesn't seem very accurate. Does anyone know
what
> the PSI range is for this check?
> Thanks for you help!
> oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
--- Mike
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