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Can?t get oil gurgle after 10 months idle

JimMac

Active Member
My RV-12 Rotax 912 has not been started for 10 months while doing ACI, brake job, satisfying SB?s, 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 ?gurgle?. Can someone explain what is going on an tell me what to do. I don?t intend to try starting the engine until I?m sure everything is back to normal.
 
First off, be sure that there is oil in the engine. :p

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.
 
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.
 
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?
 
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..
 
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.
— Jim McCarter
 
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.
? Jim McCarter
Jim,

Please follow up with us and let us know how this turns out.
 
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.
 
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.
 
I have, often on auto and tractor engines. The open valve face tends to pick up some oxidation, which allows for some leakage. I have never pulled a Rotax head but would suspect the same there. Try running a compression check on a Lycoming that has sat for a time, same effect. Compression comes up after even a short run.
.
Why would the valves not seat? Have never seen that on any auto engines that I have worked on.
 
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