Oil system air purge required?

by Nate Wetter in 912 / 914 Technical Questions 7 years ago

A few days ago we did our first oil change on our new-to-us 912 ULS. We intended to follow the instructions here, but today we looked at it again and we aren't exactly sure at what point we replaced the oil filter.

Assuming we changed the filter out-of-order, do we need to do a purge? Per the instructions, we ran the engine briefly to verify oil pressure, and yesterday I flew for an hour (before the potential issue was raised).

Re: Oil system air purge required?

by Bill Hertzel » 7 years ago

Bill Hertzel

13 1.95k 8k

No Oil purge was needed.
Any small amount of air that may or may not have been in the lines was flushed out 3 seconds after the engine started.
The Oil system moves the entire 4 liters of oil in under a minute.
An Oil system purge is performed to verify Oil Pressure.
Once you saw Oil pressure, you were done.

Bill Hertzel
Rotax 912is
North Ridgeville, OH, USA
Clicking the "Thank You" is Always Appreciated by Everyone.

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Re: Oil system air purge required?

by Roger Lee » 7 years ago

Roger Lee

131 5.38k 5.44k

You can now pre-fill your Rotax oil filter #825-016. You could not pre-fill the older one 825-012 because it had a check valve in it. Two terms. Venting and purging, Venting is rotating the prop only to help vent small amounts of air in the system like you might get in an oil change or some other small air introduction.
Purging is when you have vacated a lot of oil like a hose change or oil cooler change. It is where lots of air is introduced to the system. Venting is like when you gurgle your engine to check oil level or during an oil change.
See videos..

Venting:
https://www.rotax-owner.com/en/videos-topmenu/expanded-video-instructions/39-exp-si-27-010

Purging:
https://www.rotax-owner.com/en/videos-topmenu/expanded-video-instructions/33-exp-si-912-01813

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

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