Hi Pete,
You asked:
>Is this "wet test" the same as a compression "leak down" test?
Nope, they're different tests. The "wet test" is done just like
a regular or "dry" compression test, with the same tester. You simply
squirt a little oil into the cylinder before doing the test. Comparing
the wet and dry numbers will tell you the condition of your rings,
and if the rings are OK, that means that low compression readings are
likely to be caused by the valves (or head gasket).
>Can anyone describe how a "leak-down" test is performed and how it is
>different from a "wet test" if it IS different?
The leak down test uses a different sort of tester; it is composed
of two pressure gauges in series with a restriction between them.
One side is connected to the cylinder being tested and the other side
is connected to an air source. If you've got a leak in the cylinder
(worn rings, burnt valves, etc), you'll see a pressure difference
between the two guages. In addition, if you listen carefully, you can
usually tell exactly where the leak is. That is, you may hear a hiss
from the carbs, or see bubbling in the radiator water, or get a hiss
from the sump. If you check the engine with a leakdown tester over
time, its really easy to tell how your rings are wearing, etc. In
fact, that's exactly why I'm sold on TotalSeal rings now.
Does that make sense?
cheers,
John Lye
rjl6n@Virginia.edu
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