Oil tank empty???

by Dale Atchetee in 912 / 914 Technical Questions 12 years ago

Plane has been in the hangar for three months with no flying or running of the engine due to my foot being broken. Today went out and hand propped it and checked the oil on the dipstick. There was none!
I hand propped it quite a bit more, still no oil. Engaged the starter without running the engine several times, still no oil. Using the starter it showed oil pressure on the EIS and bled down on stopping. The oil tank is empty.
There is no oil leak, the oil has drained from the tank and has to be in the crankcase. For some reason the crankcase pressure is not pushing the oil back up to the tank. Is there now air in the system? Anybody got an idea where to go from here? Can I pressurize the crankcase and push the oil up to the tank to get the oil circulating again? It's got me stumped. The plane has flown weekly for 10 years and never went this long without running.
Dale

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Re: Oil tank empty???

by Roger Lee » 12 years ago

Roger Lee

127 5.2k 4.78k

Hi Dale,

I have seen this only a few times, but you're probably right, the oil is in the engine. Hand propping moves so little oil that you may be there for a really long time. You may be able to take off the return oil line that goes back into the tank and let it hang and get some of that oil out. You don't want to start an oil purge with an empty tank or you'll just induce air into the system. You may be able to add 3 qts. of oil to the tank and do a real oil purge and let the other 3 qts. in the engine just bleed off during the purge. It should come out very quickly. This can happen with an old style oil filter and it is also influenced by where the oil tank is in relationship to the engine in height.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell

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Re: Oil tank empty???

by Rob Seaton » 11 years ago

Rob Seaton

3 1.32k 240

You can pressurize the case; remove one spark plug, put piston to BDC (or have a large/strong person hold the prop) and gently force the oil back to the tank. Dont put too much pressure in; you dont want to blow a seal!
Rob

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Re: Oil tank empty???

by Roger Lee » 11 years ago

Roger Lee

127 5.2k 4.78k

Hi Rob,

I like to set up a camera and use a really small guy to hold the prop. It's much more entertaining! :woohoo: :lol:

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell

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Re: Oil tank empty???

by Rob Seaton » 11 years ago

Rob Seaton

3 1.32k 240

then have him hold a spark plug while you spin the engine "just to see if it is sparking"! HA! (actually I did this to myself and it was not funny)
Rob

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Re: Oil tank empty???

by Conrad Beale » 11 years ago

Conrad Beale

3 66 22

Just do a differential compression test, it will soon return the oil back to the tank...

If your oil tank is positioned high up the oil can siphon into the crankcase. This leads to some complications.
The level of oil in the crankcase can be sufficiently high that it is above the bottom of the bore. This means oil can seep past the rings into the combustion chamber which can result in a hydraulic lock. Any attempt to start the engine with oil in the cylinder could cause considerable damage.
If all the oil has siphoned into the crankcase there is virtually no oil in the tank. If the engine is started in this condition you will not have oil pressure, that is until some oil has been returned to the tank & then sucked through the pipework. There is a risk of considerable damage if an engine runs without oil pressure for any length of time.

With the high mounted oil tank you have about 2.5L of oil to return to the tank before it will gurgle & a oil level measurement can be taken. Returning the oil to the tank is achieved by gasses seeping past the piston rings & pushing the oil back up to the tank. Turning the prop slowly & pausing at top dead center allows the compressed gasses in the combustion chamber to seep past the rings into the crankcase which in turn returns the oil to the tank. The less oil in the crankcase the quicker this occurs. The higher the tank the more oil in the crankcase the longer it takes.......
It is important to check the oil level, but more importantly you need to ensure you don't have a hydraulic lock & the oil supply to the engine is not compromised.

Rotax do have limits on the position of the oil tank & if these are respected there shouldn't be any issues & gurgling should be fairly quick. If positioned outside the recommended limits (which is necessary in some installations) it may not be so easy to gurgle the oil system & accurately determine the oil level, but take care not to damage your engine if you have an installation with a high mounted oil tank....

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Oil tank empty???

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