Engine Won’t Burp

I cannot hear my engine burping unless the cap is off the oil tank.

As recommended earlier, compression leak down check OK? Collapsed oil line? Have the rubber lines been replace in the past 11 years? Crankshaft locking screw ever been removed and the sealing ring wasn’t replaced with a new one? Try a purge per Ch.79 of the IM? Otherwise a crankcase pressure test is in order.

In 500 hours of operation I have never managed to get a burp from my oil, no matter how many times I turn the propeller, even if I hold it at the peak of each compression.  I wonder if that is because the oil tank and cooler are both below the engine and the oil naturally drains back to t he tank.  Isn't the main purpose of turning the propeller to get the oil from the crankcase back into the tank?    

Bob Yanniello wrote:

Thanks for the suggestions, guys.  I’ll say right now he didn’t purchase the aircraft for other reasons, but as the owner of an RV-12 myself, but with a 912iS, my curiosity was aroused.  So, I’m quite familiar with the burping process and theory. The oil tank is in a proven position relative to the engine, the engine only has 160 hours on it - yes, 160 hours over 12 years! - so, I ruled out compression issues. And having never burped in over 12 years by multiple pilots, and pulling the prop through myself a good 20 times, very slowly, without burping, I was at a loss for an explanation.  I always check the oil after flight on mine, but since I was going to be the test pilot on an aircraft I had not maintained myself, I wanted to check oil level before taking to the sky.  So, with that extra color, any other thoughts?

The oil tank is in a proven position relative to the engine,  

I dont know what you mean by "proven position" - Rotax publish a recommended position/range. If the tank is located within this range then "all good". Outside the range, the engine may have lubrication reticulation/supply issues.

Just because an engine has low hour does not justify ruling out compression issues - just makes it less likely.

The low hours/12 years may have contributes to some internal issue - has the aircraft ever been located near the sea/or of high humidity.

"never burped in over 12 years by multiple pilots"

Was this recorded in the log book/maintenance release by the multiple pilots or was this something the vendor offered by way of explanation? You see where I am going with this?

I always check the oil after flight 

In 60 years of messing about with internal combustion engines, I have never come across a recommendation to check the engine oil after an engine has been run. There are so many reasons against this but there you go! Humans will always invent another way even when it is contra indicated/against advice and just illogical.

Ken Ryan wrote:

I cannot hear my engine burping unless the cap is off the oil tank.

This is normal - The "Burp" "Gurgle" is still there but with the cap on extremely hard to hear.