Leak From Above Starter

Discussion in 'Firewall Forward / Props / Fuel system' started by HomeBuilt101, Oct 14, 2019.

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  1. Oct 14, 2019 #1

    HomeBuilt101

    HomeBuilt101

    HomeBuilt101

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    I have a Leak-Coming IO-540 and I am trying to track down the leaks...

    It "appears" that oil is leaking from the S-Tec starter...now I know the starter does not have oil in it to leak so I get that...I looked in the Lycoming Engine Manual and it seems that there is no gasket between the starter and the engine block mating flange. I have not (yet) had the starter off so other than the black and white picture in the manual I do not know what is above the starter...

    I assume that it is the engine crankcase seam above the starter leaking and dripping down and through the starter.

    So the questions are:

    Is there some way to fix the oil leak of the crankcase seam without having to take the engine apart (silicone/ epoxy seal/ JB Weld)?

    How much oil leak is acceptable before I need to go through the hassle of engine R&R and Rebuild????

    THANKS!!!
     
  2. Oct 14, 2019 #2

    TFF

    TFF

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    Normally it’s the crank seal or case seam. Had a crank seal start spinning in the case recently. Why it never popped all the way out is a mystery. I have cleaned seams and smeared RTV or PRC on them. It usually helps. Crank seal would have to be changed to stop. In time oil will gum up the starter shafts with oil collecting dirt. The starter is all on its lonesome on a Lycoming so it can’t leak oil. Continental is opposite; starter is in oil. Make sure case halves are tight as is oil pan. Oil drain back tubes can leak on the junction air may carry to the flywheel and then drip.
     
  3. Oct 14, 2019 #3

    Dan Thomas

    Dan Thomas

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    The left front cylinder (#2) is above the starter. Its base seal can leak oil. Easier to fix than taking the engine apart, but still some work. Another, much simpler leak to fix is the #2 rocker box drain tube that runs from the cylinder head down and inboard to the crankcase. It has a flare nut on the head end and a short rubber hose with two clamps on the case end, and those things develop leaks all the time. Check that flare nut and tighten the clamps. If the rubber hose has been on there many years it's likely rotten. Cheap enough to replace. The best tool for getting at those clamp screws is a long, flexible screw bit driver. Like this:[​IMG]

    It has a 1/4" hex socket on the end that fits over those clamp screw heads. I have one I bought 15 years ago that has saved me a lot of frustration.

    Clean the engine off real good, with solvent, and dry it thoroughly. Run it for a few minutes and see if you can see the shiny spot an oil leak makes. Some engine pros use a special dye in the oil that fluoresces under an ultraviolet light to find such leaks.
     
  4. Oct 14, 2019 #4

    Toobuilder

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    If you're going through the trouble of replacing the drain tube hoses, ditch the worm drive clamps in favor of the constant tension type. These are "self adjusting" as the hose dries out and shrinks so they are an install and forget deal.
     
  5. Oct 14, 2019 #5

    Dan Thomas

    Dan Thomas

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    Like these?

    [​IMG]

    I've never, ever seen one on any of the Lycs I've ever maintained. The place they are located would make it difficult to install them. Continental uses a wire-style clamp of the same idea on their rubber pushrod tube connectors, and I have a special plier for those that still leaves plenty of misery getting them on or off, and they're a lot more accessible than the Lyc oil drain hoses. One could install those clamps at engine overhaul, maybe. Otherwise, there's a lot of baffling and plumbing in the way.
     
  6. Oct 14, 2019 #6

    narfi

    narfi

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    We put 4000hrs on 540s a year (2x twins x 1000hrs each)
    They always leak there :/
    the bottom seam down the center, and then across the front where it meets, probably 15 bolts or so total.

    It's a bandaid not a fix, but....

    Clean it super well, then clean it again, aerosol breakcleaner from napa works well and is cheap.
    Take out one bolt at a time, clean out the hole the same way, fill the hole and coat the bolt in PRC and torque it down, then do the next, etc...
    Once that is done, coat the entire seam with PRC.
    Leave it for a day with a heat lamp on it.

    A couple of thoughts if that is not the issue...
    The starter doesn't need a gasket because there arent any holes where it mounts.... its just a dry bolt on attachment.
    If I remember right your engine is facing backwards right? Follow the air flow back to the source..... that will be different for you than me.
    Two other places to check for oil leaks (though not probable from what you describe), The oil filler neck could be loose and leaking around the base, sometimes a pushrod housing seal can be pushed out and not sealing properly (or a ding/nick in a housing is spraying oil)
     
  7. Oct 14, 2019 #7

    narfi

    narfi

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    Only slightly less effective, yet easier and doesn't fill your engine with dye is using the white powder developer used for dye penetrate inspections. You clean the engine real well, then spray the developer over all the suspect areas till there is an even white coat, run the engine and oil leaks will stand out in the white like a sore thumb.

    You would not believe how hypnotic watching florescent oil drain and swirl around in a bucket under a black light at night is though..... :)
     
  8. Oct 15, 2019 #8

    Toobuilder

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  9. Oct 26, 2019 #9

    HomeBuilt101

    HomeBuilt101

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    Hi everyone,

    Sorry for the late reply...life gets in the way sometimes.

    THANKS FOR THE HELP!!!

    I will report back.
     

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