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Oil Purging

Category: 912 / 914 Technical Questions 12 months ago

I had to replace the oil pressure sender and because of the thread difference between the old sender and the new one I had to replace the oil pump housing.  after installation  I completed the oil purge procedure.  It took three rounds of purging but I finally got all the the lifters full.  I have flown 20 hours since the installation.  Two days ago while burping the engine I heard a clicking from the left rear cylinder head.  Removed the cover and checked and sure enough the intake valve lifter showed some movement and evidence that air had creeped back into the lifter.  I completed three more rounds of purging to no avail.  Any suggestions would be appreciated.  We have no local Rotax mechanics so if I cant get this fixed I will have to load the plane up on my trailer and haul to a Rotax facility 40 miles away from my airport.

  • Re: Oil Purging

    by » 12 months ago


    Are you using shop air when you purge? I know Rotax says it is optional, but I could not complete the process without pressurizing the system to 10 psi through the vent on the oil tank.


  • Re: Oil Purging

    by » 12 months ago


    My air source is a portable 40 gal compressor, which holds pressure well.  I took the line maintenance course with Lockwood in FL over a year ago. At the time I purchased all the gadgets they were selling to include the oil purge line that connects to the IN fitting on the oil tank.  When I went through this oil purge process the first time i fooled around with it but decided to do it as described in the Rotax video posted on this website which was to apply 10 PSI to through the oil tank vent line,  It took two rounds of pressurizing and finally all the valves appeared fine.  This time I made a better system to vent through the oil tank vent line but as I said, after three trys I cant get that one lift to clear.  We have no Rotax mechanics in our area that will come out to the airport.  The three main mechanics that most of the others use here refuse to touch a Rotax engine, so us Rotax guys here are kind of on our own.  I did reach out to a Rotax mechanic I met at another airport here in Maryland a few months ago and he suggest I  just keep purging, said sometimes one or two lifters can be stubborn.  Also, I was thinking about turning the engine over with the started rather than turning the prop by hand when purging, how do you feel about that?
    Thanks

    Ron


  • Re: Oil Purging

    by » 12 months ago


    I cleared a stubborn lift once by getting the engine oil up to 245 deg F for 15 minutes while the engine ran on the ground at 3500rpm withe the oil cooler mostly blocked on the air inlet side. I then let it cool overnight and checked the lifter the next morning with the engine cool and the lifter was solid. There is now over 200 hours on the engine since with no issues. 


  • Re: Oil Purging

    by » 12 months ago


    You bring up a good point.  I reviewed the video and they say to let the oil temp rise to the over 121 degree point.

    Because the oil temp does not rise sharply when the cowl is off I have not gotten the oil above 90 degrees after doing the purge proceedure.  You may be onto something here, higher  oil temp gives lower viscosity which I guess would help with oil flow at the lifter.  I will try covering the oil filter and bring the temps up over 121 and see if that helps.

     


  • Re: Oil Purging

    by » 12 months ago


    If the lifter seems marginal or you are unsure just call Dean at Lockwood and get his opinion. Thats what I did and he made me feel comfortable about how my lifter was performing with the test.


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