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Mk 25 honking/ howling noise from 1st stage help

Discussion in 'Repairing your own Gear' started by Stayingfrosty, Sep 16, 2019.

  1. Stayingfrosty

    Stayingfrosty Angel Fish

    # of Dives: I'm a Fish!
    Location: Puget Sound, WA
    8
    3
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    I was setting up my rig to help teach a class this evening and when I turned the air on for my DIN mk 25 eco it started making a droning honk noise. To rule out hose and oring extrusion I turned the air off and checked the hoses for both security and for issues with the orings and found no issues. I am assuming that there is an internal issue but there is no free flow. Any ideas about what might cause this?
     
  2. Nick Ruberg

    Nick Ruberg PADI Pro

    # of Dives: 500 - 999
    Location: South Africa
    80
    22
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    Ahh, The honking Mk25. A real plague.
    There are countless theories and fixes out there.
    Scubapro locally taught me to take the seat and rotate it by 90 degrees to see if it helps. I have had success with this in the past. They also tell me that it could be a slightly dry piston.
    One of my last services had a very stubborn honk which I couldn't get rid of until I changed the high pressure piston o-ring for a new one and this cured the problem. I saw a thread that talked about imperfect O-rings being the problem.
    I even came across a very old service bulletin from SP themselves which talked about slitting the two rings on either side of the piston seal. Don't do this.
    One of the last first stages I bought (Mk25 black) honked out of the box and the 90 degree seat trick did the job.

    The noise you hear is a flutter and the reg works perfectly well, so no worries there, but the noise will either drive you into suicide mode or the rest of your dive group into homicide mode. It is really annoying. If it just started out of the blue, it is likely a lube problem.
     
    HKGuns likes this.
  3. chillyinCanada

    chillyinCanada Solo Diver Staff Member

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    rsingler likes this.
  4. Pedro Burrito

    Pedro Burrito Moderator Staff Member

    # of Dives: 5,000 - ∞
    Location: Boussens, Canton de Vaud, Suisse
    1,870
    976
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    My MK25 started honking right after servicing. I was in the bell at Blue Grotto and another diver came in and said, “dude, your reg needs service!” I took it back three times before the technician admitted he scratched the piston and finally replaced the piston.
     
  5. Nick Ruberg

    Nick Ruberg PADI Pro

    # of Dives: 500 - 999
    Location: South Africa
    80
    22
    8
    Oh that "stubborn one" I mentioned, I indexed the seat, then changed the piston, then the seat (I had just fitted a brand new seat), then re-greased, then de-greased and eventually a new o-ring did the trick. Having said that, I have also had it where a simple seat rotation fixed it.
     
  6. Sevenrider860

    Sevenrider860 ScubaBoard Sponsor ScubaBoard Sponsor

    # of Dives: 500 - 999
    Location: Newnan, GA
    636
    302
    63
    Some things that have worked for me...
    More lube on the piston o-ring
    Rotate seat
    Change standard piston o-ring with the O2 safe version
     
  7. rsingler

    rsingler Scuba Instructor, Tinkerer in Brass Staff Member ScubaBoard Sponsor

    # of Dives: 500 - 999
    Location: Napa, California
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    As you have gathered, there is a historical issue with occasional honking in the Mk 25.
    However, it's not clear that that's what you are describing. The honk that needs seat rotation or piston replacement occurs with each (or some) breath.

    Your description suggests a honk that is ?continuous? when you turn on the air? If so, you're probably describing a high pressure leak, most likely at the shaft oring.

    You can help us with a bit more description. Consider immersing the reg and see where the bubbles come from. There are a couple more tricks we can give you to diagnose, but it sounds like this reg needs a teardown and service.
     
    couv likes this.
  8. fmerkel

    fmerkel Loggerhead Turtle

    # of Dives: 1,000 - 2,499
    Location: Salish Sea (Seattle)
    1,588
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    I have a MK15 that has had a honking problem. Putting in a poly O-ring stopped it for several months. Lube did not. Came back, but only when tested above water. Below water it's fine.
    My wife's MK 20 (similar guts) has occasionally been a bugger with this. Lube and O-ring change did not work for that. Changing the little plastic piston supports did.
     
  9. Stayingfrosty

    Stayingfrosty Angel Fish

    # of Dives: I'm a Fish!
    Location: Puget Sound, WA
    8
    3
    3
    @rsingler, Yes, you are correct it is a continuous noise once the air is turned on. prior to submerging the first stage it hissed for a second and then it started to squeal/whistle/honk from the first stage once I hit the purge button on one of the second stages. I could feel air coming from the openings on the regulator body so i know that there is a leak in there some where. I agree it needs to be overhauled is there anything in particular that I should be looking out for on a specific part that might need replacement or repair aside from the shaft oring? Thanks for all of the responses and advice.
     
  10. lexvil

    lexvil Loggerhead Turtle

    # of Dives: 1,000 - 2,499
    Location: jamestown, ca.
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    Did you submerge it or just feel air coming out?
     

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