Quote:
Originally Posted by rtanner
its the way its done,
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Quote:
Originally Posted by hurryinhoosier62
You use the oil to seal the rings AFTER you have established a base line reading. IF the pressure goes UP, the rings aren't sealing correctly. If it stays the same or DECREASES, start looking for leaking valves(especially exhaust valves). We've been doing this for DECADES on recip aircraft engines.
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1. How can adding oil decrease the pressure? What in a combustion chamber leaks MORE when oiled?
2. The FAA does not suggest a "wet" leakdown test where oil is added to the cylinder via the spark plug hole. They do accept an "oiled" re-test that involves running the engine in "CHAPTER 8. ENGINES, FUEL, EXHAUST, AND PROPELLERS; page 8".
http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/list/AC%2043.13-1B/$FILE/Chapter%2008.pdf
Quote:
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Originally Posted by FAA
recheck the readings after operating the engine for at least 3 minutes to allow for sealing of the rings with oil.
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My concern still stands: Does added oil via the spark-plug hole just blow out the ring gaps or other ring leakage points when the cylinder is pressurized? The result would be no difference in "wet" versus "dry" cylinder leakdown testing once the oil has moved down the piston.