Craig,
What a great tool for diagnosing an engine!! Where can I get one? Sounds
like basically a pretty simple device, except you need two pressure gauges.
Do they normally come with the gauges too, or do you need to supply your own?
I guess if you start a long way from TDC the valves open, and if you're
real close to TDC, but not exactly the pressure pushes the piston down to
BDC. Maybe, for this reason, you should put the engine in gear each time
you do the test to keep this from happening. Also, the fourth place to
listen I suppose is in the valve covers in the case that the valve guides
are loose.
Thanks for the interesting tip,
Bob
At 08:53 PM 8/31/99 -0700, Craig Wright wrote:
>Bob,
>
>That sounds like a lot of work. I've been using a leak-down style tester
>that is
>only a little more cumbersome to use. The major effort to use it is to
>ensure that
>the cylinder under test is at TDC-compression. I detected a very bad leak
>in two
>exhaust valves before I noticed any performance degradation. The gauge uses
>compressed air. (I use 80 psi since that is what airplanes use and I am
>familiar
>with the numbers.) The cylinder is pressurized through a small orifice.
>There are
>two gauges on the unit, one reads applied pressure and the other reads the
>pressure
>in the cylinder. The difference is lost due to flow through the orifice
>caused by
>the cylinder leaking. If the cylinder is perfect, the pressure is the same
>on both
>gauges. On aircraft anything above 70 is considered very good, 60-70 is
>OK, and
>less than 60 is suspect. My two bad cylinders read 5, yet it still ran OK,
>although
>it wouldn't for long. Another advantage is that you can listen in the intake,
>exhaust or engine breather to determine what is leaking.
>
>Craig
Robert L. Palmer
UCSD, Dept. of AMES
619-822-1037 (o)
760-599-9927 (h)
rpalmer@ucsd.edu
rpalmer@cts.com
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