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Help Need advice fixing threaded oil pan

Discussion in 'Suzuki 250cc Twins' started by Matchbox, Dec 23, 2020.

  1. Matchbox

    Matchbox Member

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    Hi everyone,
    I have done the noob mistake of crossing threading my oil drain plug threads.

    Now I have used a ST14x1.5 HSS tap and installed a helicoil.

    Made the mistake of buying 1.5mm instead of 1.25mm resulting in having to buy a new oil drain plug.

    I get perfect seal with the washer and new plug for about 2 weeks, it will slowly loosen over time, will not drip oil only seep out over time enough to cover the drain plug, some reason it wont drip on my garage floor and right after a long ride so I must be doing the job 99%.

    Research I have been doing people have said using a carbon steel drain plug will expand faster eventually will loosen over time ?!?

    Seems to be my problem.

    Wondering if I should get a aluminium plug and that will solve my issue?

    Or pull out the helicoil and use a bigger bolt on the fresh threads?

    My original suzuki m14x1.25mm plug had no washer on it but got a good seal...better to use no washer?

    First 2 photos are fresh installed plug/washer with helicoil.
    Third photo is first helicoil install attempt - corrected on second by cutting length down.
    Last photo is fresh tapped threads without helicoil - tap ST14x1.5 - not sure what bolt size I would get for this as m14x1.5mm is the internal diameter of the helicoil.

    Merry Christmas![​IMG][​IMG][​IMG][​IMG]

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  2. Gen

    Gen Well-Known Member

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  3. Murdo

    Murdo The Good Doctor Staff Member Contributing Member Ride and Events Crew

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  4. jmw76

    jmw76 Well-Known Member

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    Have you tried a new copper washer?
     
  5. Matchbox

    Matchbox Member

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    Thank you all for the advice!
    Yes a new copper washer every 2 weeks haha
    I've had another look and noticed I have nicked a very small piece about 2x2mm of the casing out when removing the first helicoil resulting in not a perfect edge that meets the flat side the washer sits against. Hopefully a little dot of jb weld can fix it.
    I could tap up a size or two making a good edge again.

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  6. Zippy

    Zippy Active Member

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    Hey Matchbox, I'm currently feeling your pain when it comes to leaking oil pans!

    My bike came with a non-standard sump plug and washer, which leaked.

    So I replaced them with the original Suzuki items.

    original.jpg

    Tried an original washer, twice. The second time I added PTFE tape, but that's more hassle than it's worth.

    Notice how the washers have deformed after being installed, which makes me think the design is effective in theory.



    As Murdo recommended above, I then tried a 'dowty' washer.
    The idea is it seals better than metal alone by using bonded rubber.

    dowty.jpg



    I then tried a 'stat-o-seal', which looks to be a brand name item from Goodridge.
    The idea is that when tightened, the metal washer clamps in against the bolt threads and seals even more effectively than a dowty washer.

    stat.jpg




    I then found what I thought would be the answer - a slightly over-sized drain plug with a piggy-back drain bolt. The idea is the shape/size of the threads cut a new mating surface in the pan and stays there, with the smaller inserted bolt being your new drain plug!

    over1.jpg

    This was hard to find because, like you've found, drain bolts and particularly over-sized drain bolts usually come in 1.5mm thread and 1.25mm is less common.

    As you can see, the stay-in bolt managed to find and remove some sealant that must have been on the oil pan threads that I didn't even know was there! This wasn't apparent when using the regularly sized drain bolts.

    over.jpg

    So it looks like it would have been effective and is perhaps a way of saving your original pan threads before taking the next step. You could therefore use an over-sized / piggy-back bolt in 1.5mm variety and hope it works in your current situation.



    To explain my predicament... none of the above stopped my slow oil leak because on closer inspection, the pan has a hairline crack around the drain hole!

    crack.jpg

    Therefore where I thought I was dealing with just a dodgey drain bolt or washer or slightly knackered oil pan threads, turns out I was never going to win.

    So hopefully the above is of help / interest!

    To everyone else, please don't overtighten your oil drain plugs. If not for your benefit, then for the poor sap who owns the bike somewhere down the line!

    :mad:
     
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