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  1. #1

    Mystery Hynautic Air Leak

    1986 63MY. Vessel has Hynautic throttle and shift controls. Port side will leak from 80 psi to 0 in about
    72 hours. Been doing this since I purchased 4 months ago. Works fine other than leak.

    Fluid is not leaking anywhere and fill level has remained constant in reservoir canister, so assuming it
    is an air leak at the top of the reservoir. I have replaced schraeder valve, added teflon tape to both
    schraeder valve fittings. I am not able to remove pressure gauge without breaking reservoir from
    ER bulkhead. No change. I have used soapy water twice on all fittings on top of canister. No bubbles
    observed. Suggestions requested!

    Is there something better than (dish detergent) soapy water to located a VERY slow leak? It seems to loose foaminess
    quickly. I suppose my next
    step is to remove canister, pressurize and submerge in bucket of water.

    John McCarley
    Water Colors
    Wrightsville Beach NC

  2. #2

    Re: Mystery Hynautic Air Leak

    I had the same issue twice before, both times it was the gasket on the top of the reservoir, I guess they dry out as they don't get wet very often. They make a rebuild kit for those. It's not a big deal to DIY......Pat

  3. #3

    Re: Mystery Hynautic Air Leak

    Thanks. To clarify, are you referring to the o-ring at the fill cap or at the top of the round canister where
    it meets the lid (top plate)?

    John

  4. #4

    Re: Mystery Hynautic Air Leak

    yessir!!

  5. #5

    Re: Mystery Hynautic Air Leak

    Home Depot sells an all purpose leak detector, brand name "Oatey", claims to make "big bubbles for even the slowest leaks". Under $5 I'm sure there's others like it.
    1978 53' Motor Yacht "LADY KAY V"
    Hull number 524
    Chesapeake Bay

  6. #6

    Re: Mystery Hynautic Air Leak

    Airconditioning and refrigeration supply shops sell a liquid product called microleak detector. Comes in a spray bottle.
    +++
    1984 61MY #353 with 9' cockpit extension.
    Sydney, Australia.

  7. #7

    Re: Mystery Hynautic Air Leak

    Used the leak detector and nothing found. Cannot really test gauge with leak detector without tearing gauge apart. Will replace gauge and try test again. After that, I'll rebuild the canister unit. Having to defer work until we get through Dorian.

  8. #8

    Re: Mystery Hynautic Air Leak

    Ensure you put pressure back in the system. I've used dish soap and look for bubbles

  9. #9

    Re: Mystery Hynautic Air Leak

    Have pressurized to 80psi and searched with dishwashing liquid/water 3 times. No Joy! Now, when I
    re-pressurize the throttle (both helms) is spongy feeling; moves forward but returns to idle position. I think Ill call technical
    support.

  10. #10

    Re: Mystery Hynautic Air Leak

    Quote Originally Posted by divert00 View Post
    Have pressurized to 80psi and searched with dishwashing liquid/water 3 times. No Joy! Now, when I
    re-pressurize the throttle (both helms) is spongy feeling; moves forward but returns to idle position. I think Ill call technical
    support.
    Don't want to be the bearer of bad news but Hynautic has been out of business for quite a while so tec support is hard to come bye.
    Best place I found for all hydraulic repairs is in Florida http://www.boatsteer.com/
    T
    hese people are the nicest and fastest service for Hynautic steering and shift problems and stock tons of parts. If they don't have the parts they can make them. Suggest calling them for advice on where to look first.

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