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Thread: My 0470 leaking at taxi.

  1. #1

    My 0470 leaking at taxi.

    I have a question about an oil leak that I found on my airplane last week. The plane has 700 hours on a 470. I put my first quart in it after 11 hours of flight. I added this quart a week ago. Iím not a pilot yet but Iím able to taxi the plane at my airport. So I just taxed it a couple places At the airport and did not fly it and I noticed I had oil splotches on both sides of the fork on front. Had me concerned I stop by A mechanic shop. After taking the decal and running it they claim itís valve guides which heís got me stumped. The oil seems to be dripping out of the air induction system breather. The plane was five in North Carolina last August. The original oil is in it which is 15- 50 Aero Shell. Iím changing that to 100L At my annual in August. In fact Iím going to hold off until that annual to really do a through check Of the motor. Iíve been flying it consistently the last 5 weeks and iím ready to solo. Been working in the plane pretty hard take offs landings in the 90s so weíve been watching the heat gauge but never seen it overheat. But this oil leak is got me somewhat worried. The mechanic claimed he needed the pull some jugs to figure out where itís coming from he young and Anxious. I said let me think about it because that is a big move. It actually made them mad at me and Iím not gonna take my plane back there again. Also they claimed it takes 11 hours per Jug to investigate at $100 a hour l. I Have the right to think about it. Itís nowhere around the jugs that itís leaking. The valve covers are dry. Some oil is back toward the accessory box and may be a little bit coming from the Air pump. With the Cowl off They started it and ran it And they said the oil was dripping into the induction system and out the air breather which may be an indication of s valve guide. What do you think? The mechanic said just fly it and watch the oil level. The last time we put flew there was no leakage that I noticed after 1 1/2. I havenít flown it since I finally saw this leaking during my taxi since Iím not a pilot. My instructor will be back next week and will go up one hour landed and investigate to see whatís going on. Hopefully not a whole lot. I guess all I did today was taxi it but not take it to flight. Maybe it was a cumulated oil that finally showed up because I did not take it to fly. Your opinion since I know youíve worked on a lot of these. The engine have 700 hours on a rebuild that took place 8-10 year. s ago. Itís a 1956 Cessna 182

  2. #2

    Join Date
    Oct 2011
    New Hampshire
    Wow, no one has spoken up.

    My experience with a number of hours behind Continental O-470's is that they hate to be run cool. Taxiing around does the engine no favors. Neither does doing touch and goes. You get lead in the valve guides. The 6 cylinder Continentals like to be warmed, driven along at constant 65-75% power for hours, then shut down. Operate too cool you get lead in the valve guides, not real hard to deal with (think "rope trick"). To hot (skydiving and glider towing) and you get carbon in the piston ring lands. Much more expensive to fix (think pull cylinder).

    As for oil appearing to leak from the accessory case area, I would start by replacing the AN900 gaskets for the oil screen and looking at the gaskets around the drive for the aft generator or alternator. The mags are facing forward do those gaskets leaking would show up on the upper case.

    They make cool kits that put a dye in your oil that shows up when you shine an ultraviolet light. Cleaning the engine so that it is spotless, adding the dye, then flying for a half hour before inspecting might tell you something interesting.

    Best of luck,


  3. #3

    Join Date
    Aug 2013
    Gwinn, Michigan
    How much oil is in the engine ? I have found that Continental engines tend to "get rid of" oil that they don t want. I have found they are happy with 8 to 10 qts. Another thing I noticed, 700 hours on an 8 year overhaul. Clean that engine , take it on a long flight and check it afterwards. A lot of O 470 engines also have an air /oil separator installed, I have found that is a good place to look at also. Where does it exit from cowling ? Could be blowing into cowling. Just as a guess.

  4. #4
    Dana's Avatar
    Join Date
    Jul 2011
    I'm not familiar with the big Continentals but the induction system (carb, air box, and intake manifold) is completely different from the breather, which is a crankcase vent. Some oil out of the breather is not uncommon, especially if there's no oil separator and/or the crankcase is full. On my Lycoming, even though it holds 8 quarts anything over 5 goes right out the breather.

  5. #5
    I have an IO-470 which I believe leaks some oil passed the intake valve guides. In my airplane there is a DRAIN on the induction system, as I believe there is on most airplanes. It is there in case excess fuel gets into the induction system from over priming. It sounds like you have a similar problem of oil leaking passed the intake guides and down the drain of the induction system. First, airplanes leak oil. So long as it is not excessive, it's not a problem (in my opinion). Second, if this is not the source, you need to figure out where it is exiting the engine. Then you can determine if it is a problem.

  6. #6
    Oh, bye the way, running the engine at idle for a long time is likely to create the most leaking from the intake valve guides as the oil is being sucked at high vacuum from the valve cover area through the guides to the intake ports.

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