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912 Oil Change gone bad

in 912 / 914 Technical Questions 12 years ago
Help! While changing oil on my 912 I apparently drained oil from more places than I was supposed to and now I can’t get oil pressure when the plane runs. I followed the purge instructions using air pressure on the canister and turning the prop and that didn’t work. If I run it I still only get a reading of about 8-10 lbs. Does anyone know how to resolve this at this point? Any advice would be greatly appreciated.

  • Re: 912 Oil Change gone bad

    by » 12 years ago

    Hi Steven

    DONT start your engine again until you have good oil pressure. You will do a lot of ***VERY*** expensive permanent damage. If you follow the oil purge procedure and don't be in any rush, it will work. If you pressurise the tank it will push oil to the pump which will then pump it around the engine and then build up the pressure. Make sure you take the spark plugs out which will make it easier to turn the engine over and reduce the load on the bearing shells. It can take a lot of turns to get pressure but it will work. Persevere, it will be worth it.

    Mark
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  • Re: 912 Oil Change gone bad

    by » 12 years ago

    Thank you for the advice. I have run the engine a few times for 10-15 seconds (after the purge procedures)so I sincerely hope I haven't wrecked anything. I do think I found the problem. When I was changing the oil I opened the pressure release nut (I know, very stupid) and some oil gushed out along with the spring, and apparently the plunger and ball, which I missed. I had put it back with just the spring. I looked at the schmatic this morning and pulled the nut again and the the punger and ball were missing. I assume that's why the purge procedure didn't work. Without the punger the pressure release was wide open and therefore pressure couldn't built. Anyway, i ordered the parts (I couldn't find them). Once I get them in I'll do the purge procedure again. What should I expect for a pressure reading turning the prop before I try starting the engine again? Am i correct that I will have to check the tappets as well? Is there anyway to tell if the engine's been damaged? Steve
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  • Re: 912 Oil Change gone bad

    by » 12 years ago

    Hi Steve,

    You will only need a plunger or a ball, the ball is the old type of valve, the plunger is the new type, so you will have a plunger, spring, and bored out hex head screw, or ball, spring and bored out hex head screw.

    When you purge it you should get at least 2 bar or more spinning the prop by hand, it may take some time so just bear with it. If the oil has drained from any tappets you will hear them while turning the prop. If you do they should go quite as the oil pressure starts to build. Only when you have good pressure should you run the engine. It will be worth doing a tappet check as it demonstrates in the video as it only takes a couple of minutes and confirms the tappets are free of air. You can probably get away with not changing the O-rings in the rocker covers.

    Take your time and you will be OK, but don't run it again until you have good oil pressure turning the prop by hand.

    Cheers Mark
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  • Re: 912 Oil Change gone bad

    by » 12 years ago

    Steve,

    If you only ran the engine 10-15 seconds there is a good chance you did no damage. No way to check internally without disassembling the engine. Could you hear the valves pounding when you ran the engine? It would have been like a loud rattling noise. If not, that is a good sign. You can check the valve spring support washers for visible signs of wear from pounding. That is about the easiest thing to check after a pressure failure but even that requires removing the rocker arms and valve springs and a dial indicator to measure the washer thickness. I believe I would do what Mark suggested first. Refit the ball and spring and do the purge again. Sometimes it takes a lot of hand cranking, but the pressure will come up.

    Bill.
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  • Re: 912 Oil Change gone bad

    by » 12 years ago

    Thank you both very much. The engine sounded just fine when I ran it, so knock on wood. I do have a question. I ordered both the ball and the plunger, not knowing any better. Does it matter which one I use when I put it back together?
      
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