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  #1  
Old 06-06-2018, 08:35 AM
JimMac JimMac is offline
 
Join Date: Jun 2012
Location: Madison, AL
Posts: 61
Default Canít get oil gurgle after 10 months idle

My RV-12 Rotax 912 has not been started for 10 months while doing ACI, brake job, satisfying SBís, etc. l recently thought it would be a good idea to turn the prop by hand to pump the oil back into the oil canister. (A fresh oil change was done just before my final flight 10 months ago). Well, the first thing I noticed when I started turning the prop was that the engine compression seemed low. I kept turning the prop - about 100 revs - and I never could get the ďgurgleĒ. Can someone explain what is going on an tell me what to do. I donít intend to try starting the engine until Iím sure everything is back to normal.
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  #2  
Old 06-06-2018, 09:41 AM
DHeal DHeal is offline
 
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Location: Windsor, California
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First off, be sure that there is oil in the engine.

Second, be sure you are pulling the prop through relatively slowly with a 2-3 second pause at the point of each cylinder's maximum compression -- quickly rotating the prop delays the gurgling process.

You could perform an oil system purge (the process is described in the ROTAX service manuals) to ensure that there is no unwanted air in the system and that the oil is properly flowing.

After the purge, you could remove the top spark plugs and quickly turn the prop by hand -- you should see oil pressure registering on the oil pressure gauge.
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  #3  
Old 06-06-2018, 09:46 AM
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Phantom30 Phantom30 is offline
 
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As David has suggested...do an oil purge per Rotax service buliten (your valves are probably not sealing...hence, no compression. Which is needed to return oil to tank.
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  #4  
Old 06-06-2018, 09:48 AM
Mich48041 Mich48041 is offline
 
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Do not turn the prop fast. Turn it slowly until at the top of a compression stroke, then pause for a few seconds, then repeat, pausing at the top of each compression stroke. The pause gives time for air to leak past the piston rings and pressurize the crankcase. The pressure in the crankcase will push oil out and into the tank. Does any oil show on the dipstick?
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  #5  
Old 06-06-2018, 11:19 AM
DHeal DHeal is offline
 
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Jim --

I trust that you know NOT to turn the ROTAX 912's propeller backwards any significant amount. Doing so has the potential to introduce air into the oil system -- not a good thing.

BTW, the ROTAX Service Instruction for oil system purging can be found at:
https://legacy.rotaxowner.com/si_tb_...-912-018r2.pdf

-- David
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  #6  
Old 06-06-2018, 11:52 AM
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DonFromTX DonFromTX is offline
 
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Even following all the previous tips, it took FOREVER for mine to gurgle after sitting for some months. I think that the valves don't seal quite as good after sitting, and therefore the crankcase pressure is less than normal getting by the rings..
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  #7  
Old 06-06-2018, 05:23 PM
JimMac JimMac is offline
 
Join Date: Jun 2012
Location: Madison, AL
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Thanks for the tips guys. I’ll try again and follow your suggestions. Yes, I do know not to turn the prop backwards. And I’m sure there is a full load of oil in the engine. I made only 1 short flight right after an oil change and there have been no oil leaks, so it has to still be in there. I think I WAS turning the prop too fast. I’ll slow down next time.
I’m not sure what the oil purge is suppose to do for this problem.
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  #8  
Old 06-06-2018, 06:58 PM
Driftdown Driftdown is offline
 
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Quote:
Originally Posted by JimMac View Post
Thanks for the tips guys. Iíll try again and follow your suggestions. Yes, I do know not to turn the prop backwards. And Iím sure there is a full load of oil in the engine. I made only 1 short flight right after an oil change and there have been no oil leaks, so it has to still be in there. I think I WAS turning the prop too fast. Iíll slow down next time.
Iím not sure what the oil purge is suppose to do for this problem.
ó Jim McCarter
Jim,

Please follow up with us and let us know how this turns out.
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  #9  
Old 06-07-2018, 10:24 AM
EXflyer EXflyer is offline
 
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Location: Chiloquin OR
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Quote:
Originally Posted by DonFromTX View Post
Even following all the previous tips, it took FOREVER for mine to gurgle after sitting for some months. I think that the valves don't seal quite as good after sitting, and therefore the crankcase pressure is less than normal getting by the rings..
Why would the valves not seat? Have never seen that on any auto engines that I have worked on.
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  #10  
Old 06-07-2018, 02:43 PM
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Piper J3 Piper J3 is offline
 
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Quote:
Originally Posted by EXflyer View Post
Why would the valves not seat? Have never seen that on any auto engines that I have worked on.
I think the reference was to lifter bodies pumping up with air if oil not purged correctly. You'd have to draw air into oil pump/pressure galleries.
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