Mercury KD-4 Cast Aluminum gas tank seam leak

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  • Buccaneer
    Buccaneer

    US Member - 1 Year
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    #191855

    I replied to a year old thread of Louis “Green Thumbs”, but it doesn’t appear that
    replying to an old thread “brings it to the head of the queue. Therefore, this is
    for Louis or anyone else that’s attempted repairing a seam leak on the KD-4 style tanks.
    ——————–
    Louis, I’ve been reading your old thread on fixing up leaking Mercury cast aluminum tanks.
    I have a KD-4 that’s weeping along the seam.

    Just wondering how all your hard work turned out when the tanks had the
    test of “time and gasoline” in them?
    Wondering if I should follow your path you outlined nicely, or buy some gas
    tank sealer?

    No idea if my tank bolts will turn, and if they don’t, I’m hesitant about breaking
    any off…….. I have no milling machine! The tank has gas in it now, so
    torching the bolts may be an issue as well!
    Thanks.

    The KD-4 in question running last October…..

    Prepare to be boarded!

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    green-thumbs

    US Member - 1 Year
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    #191888

    I have been into about a dozen of the cast aluminum tanks, I was very fortunate to run into the easy to do ones first. Later on I rand into tanks
    with warped or corroded flange surfaces, broken studs and shut off
    valve. All problems were resolved and tanks resealed.
    Did I know what I was doing when I started…nope…had to figure things
    out as I went along. Sometimes you do need a welder to add back a little metal to repair a crack or fill in a drilled out stud hole or gas valve hole
    I have the advantage of a lot of odds and end collected over the years;
    The motto in my shop is “What would McGyver do?” Junk I picked
    up decades back sometimes is just the right thing to solve a problem…
    sometimes the first solution proves unworkable, but, in the attempt
    the solution that will work becomes clear.

    How long will the reseal hold up over time? I don’t know, probably long
    enough to outlast me. I think it will depend upon my workmanship more
    than material used, I have had to redo a tank that failed to seal the first
    time ,but, that was due to an error on my part.
    Currently I am working on a cast aluminum tank from a 1941 Sea King
    single made by Kiekhaefer. I have it cleaned up and tank flange surfaces sanded flat and smooth. Sometime in past its had a seam
    leak repair attempt…drilled 2 holes thru tank halves from top to bottom
    Threaded rods were used to pull tank halves together in an effort to
    stem the leak. A different way to do things, but, if it solved the seam leak it also made for 4 new ways for tank to leak.

    Louis

    • This reply was modified 2 weeks, 1 day ago by Avatargreen-thumbs.
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    green-thumbs

    US Member - 1 Year
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    #191893

    I do not know how long reseal will hold up. I suspect workmanship matters more than material. Kiekhaefer sealed tanks have held up very
    well as most do not leak even after 7 or 8 decades
    The 1941 Sea King tank in photos shows evidence of a repair method
    not often seen. The holes drilled thru the tank had threaded rods to draw
    ends of tank together…may or may not have worked. One thing certain.
    it made for 4 new places to leak.
    The other tank is an early pattern without the fore and aft hex
    head screws and a small boss for gas shut off valve. Could be for a
    prew war or early postwar twin with a rope plate starter.
    Resealing a leaky tank seam by splitting the tank, removing old gasket
    and sealant, cleaning and if needed sanding tank flanges level is low
    tech and low cost. It can get a little hairy if your break a stud, not the end of world, just more work, If anyone is interested I have a photo
    series of how to drill out a stud broken off flush. McGyvering at its best,
    Louis

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    Buccaneer
    Buccaneer

    US Member - 1 Year
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    #191914

    Thanks for your reply.
    I was confounded looking at my tank and seeing only four fasteners that are
    suppose to keep the whole seam from leaking. Wonder what they used
    75 years ago for a sealer…. must have been good stuff!

    Prepare to be boarded!

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    green-thumbs

    US Member - 1 Year
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    #191924

    Kiekhaefer cast aluminum gas tank evolved, apparently in response to problems with early tanks, The twin tanks come with and without the fore
    and aft hex socket screws. several variations of fuel outlet boss, and
    perhaps a bit more metal here and there. Rewind starter requires 4 screw holes in upper tank half to mount starter.
    Tanks for single cylinder models also have variations.
    We are probably better off not knowing what went into tank sealant and
    gasket. I assume the worst and work and work over wet newspaper
    when removing old gaskets then wet mop,
    Louis

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    billw

    US Member - 2 Years
    Replies: 1082
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    #192058

    I will just add my two cents to this. When I split my tanks open, I take them to an automotive machine shop. They have a giant, horizontal belt sander. It’s very purpose is to true up slightly warped parts. I give the guy twenty bucks and the tank halves are as true as the day they were made, in about five minutes. Also, the last tank I did was a WD3S Wizard. Rather than fuss with a gasket, I tried an experiment and used that red, jelly donut-like, anaerobic sealant, the same stuff used on crank case halves. It is known to stand up to ethanol, at least as good as anything can. I let it set up for a week, just to be sure to give it the best chance at success. I ran the motor at the Lowell Mass meet in September, for at least an hour straight, with no leaks evident. Going forward, I think I will do this again. It was much easier than the gasket method.. It “seams” to work, if you’ll pardon the pun.

    Long live American manufacturing!

    • This reply was modified 1 week, 6 days ago by Avatarbillw.
    Buccaneer
    Buccaneer

    US Member - 1 Year
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    #192063

    Bill, thanks for your input. First I’ll see if I can get the bolts or nuts to budge that
    hold the tank together. I know of no big belt sander in these parts, but wish
    I had one bigger than my 4″ a few times!

    I’ve had good luck so far with “gas tank sealer”, and if planned ahead, a
    little $25 can could be used to seal two or three tanks, so that’s always
    an option as well if things aren’t going well taking the tank apart.

    While lying in bed, I was wondering about omitting the gasket as well,
    and using something like Yamabond 4 sealer, for the crankcase halves. Not sure
    what it’s specs say about gasoline though.

    Prepare to be boarded!

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    green-thumbs

    US Member - 1 Year
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    #192092

    There are several ways to skin a cat…the method I use involves old school technology, I have run into a tank sealed only with a sealant without gasket. Strong bond and it did not leak, but, tank was damaged
    so it had to be split to repair. What ever it was it did a GREAT job.
    I have also had a tank with all seams welded…that one would never
    leak. Some attempted remedies for a seam leak failed to solve the
    problem or introduced new problems.
    Louis

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    green-thumbs

    US Member - 1 Year
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    #192253

    What do you do if you snap off a stud while splitting open
    a cast aluminum tank.. out of the box thinking required
    Fasten tank halves together using the other
    bolt holes. Make a snug fitting drill sleeve to guide
    drill into broken off stud….I used several different
    sleeves to drill successively larger holes.
    CHECK what drill is doing by taking tank apart
    to be sure drill is not wondering.
    Do NOT drill into threads.
    Tap new thread also using tank to align
    tap so it creates a thread straight and true.
    I did not attempt to back out the remains
    of stud. I had used up my supply of good luck
    getting things acceptable…going for perfect
    involved risking all I had gained.
    Louis

    • This reply was modified 1 week, 4 days ago by Avatargreen-thumbs.
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    Buccaneer
    Buccaneer

    US Member - 1 Year
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    #192260

    Good idea Louis using the guide and tank top for drilling alignment.
    I have not tried anything on the tank yet, but plan it after I’m done
    with the lower unit. Thanks for sharing.

    Prepare to be boarded!

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    green-thumbs

    US Member - 1 Year
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    #192264

    Fun if everything turns out right and PITA if they do not.
    Check, check and recheck as you drill.
    Use good drills, Not so good drills give not so good results.
    You get one good shot at getting it right.
    Leave nothing to chance
    If it is not going as hoped, STOP and study
    the situation. If things are going bad, going ahead
    usually makes things worrse not better.
    Louis

    Buccaneer
    Buccaneer

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    #192265

    Louis, good advice for pretty much everything in life!

    Fun if everything turns out right and PITA if they do not.
    Check, check and recheck as you drill.
    Use good drills, Not so good drills give not so good results.
    You get one good shot at getting it right.
    Leave nothing to chance
    If it is not going as hoped, STOP and study
    the situation. If things are going bad, going ahead
    usually makes things worrse not better.
    Louis

    Prepare to be boarded!

    Tubs
    Tubs

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    #192301

    Buccaneer
    Buccaneer

    US Member - 1 Year
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    #192302

    I just pulled the tank apart a little while ago, after I let it sit
    in the wood stove “hot air” pipe for about an hour.
    It came apart relatively easy, though I have not tried turning
    the studs yet, nor have I looked for some thick glass to
    use for lapping the tank halves.

    DSCN8591

    DSCN8595

    Prepare to be boarded!

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    green-thumbs

    US Member - 1 Year
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    #192314

    Treat the studs as if you know they will snap if forced, Putting a pipe wrench on them will work IF they are in the mood to be cooperative.
    AND a very BAD idea if they are stubborn. It seems to me you have
    gotten past the hard part, with some careful use of torch and gentle
    persuasion, I think studs will be cooperative,
    The studs are 2 long and 2 short, I have, in past ,attempted to reseal with studs in wrong sport…oops!
    I use the mirror door from an old medicine cabinet… metal back and
    band around edge ,seem much safer than a piece of plate glass.
    Found in trash many years back, kept it ,as something too good to
    throw out , only took 25 or 30 years to fine a use for it…spent about 3
    weeks looking for it when I realized its time to be of use had arrived.
    Louis

    • This reply was modified 1 week, 3 days ago by Avatargreen-thumbs.
    • This reply was modified 1 week, 3 days ago by Avatargreen-thumbs.
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