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  #1  
Old 03-09-2017, 08:36 PM
RFSchaller RFSchaller is offline
 
Join Date: Oct 2010
Location: Phoenix, AZ
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Default Bonehead move on compression test

I'm doing the 5 year rubber replacement, so I have a lot of stuff removed to gain access to hoses. That includes the oil tank. Yesterday I decided to do the compression test with the oil tank hoses disconnected. Bad decision! Blew oil all over the place! Pretty good lesson on the effectiveness of piston ring blow by as opposed to a scavenger pump!
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  #2  
Old 03-10-2017, 10:20 AM
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Jetguy Jetguy is offline
 
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Location: Texas, Fort Worth
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Quote:
Originally Posted by RFSchaller View Post
I'm doing the 5 year rubber replacement, so I have a lot of stuff removed to gain access to hoses. That includes the oil tank. Yesterday I decided to do the compression test with the oil tank hoses disconnected. Bad decision! Blew oil all over the place! Pretty good lesson on the effectiveness of piston ring blow by as opposed to a scavenger pump!
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  #3  
Old 03-10-2017, 02:14 PM
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Piper J3 Piper J3 is offline
 
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Are you cranking the engine or using differential-pressure tester?

DP is much safer and allows better diagnostics to determine if leakage is ring or valve related...
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  #4  
Old 03-11-2017, 10:26 AM
RFSchaller RFSchaller is offline
 
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I use the DP method. The oil blew out the return line as soon as I applied air pressure to the cylinder.
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  #5  
Old 03-11-2017, 07:18 PM
R100RS R100RS is offline
 
Join Date: Jan 2014
Location: USA
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Yes, with the DP method, a loud gurgling (as occurs when the 912 engine is "burped") is audible when the cylinder is pressurized (just remove the oil tank cap to hear it quite clearly).

Last edited by R100RS : 03-11-2017 at 07:20 PM.
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