Quote:
Originally posted by 911pcars
Leakdown percentage change from 25% to 0% (cold to hot) begs the question as to the method you used to determine leakage.
Not sure any engine can have 0% leakdown, but others can confirm their experience.
Sherwood
http://members.rennlist.org/911pcars
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Sherwood,
Excellent question. As I mentioned I performed the first test erroneously. My tester has a check valve of sorts that has to be compressed to allow air in or out. I was pressurizing the gauge and setting to "zero", and THEN compressing the check valve thereby filling the last 6" of hose and combustion chamber with air. This process resulted in a 15% to 25% drop on the gauge.
When I correctly set the gauge with the combustion chamber pressurized, I could detect no leakage while holding it for 20-30 seconds. To verify my method, I tested the gauge with the hose venting to the atmosphere (instead of combustion chamber) and the gauge steadily dropped to about 30-40% after 20-30 seconds.
I suppose I could still have an oil ring issue but it appears that the compression rings and cylinder bores are okay.
A teardown seems inevitable but how much and how soon it needs to be done are things I'd like to get a better feel for. Since my budget won't allow a serious teardown with headwork etc. right now I'm really trying to determine whether I need to park it or continue driving it (about 200 miles per month).
Sorry for the long-windedness (is that a word?).
Thanks.
David