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Mk25 - query on a slight post service problem

Discussion in 'Regulators' started by cbanhidy, Jun 17, 2012.

  1. cbanhidy

    cbanhidy Angel Fish

    # of Dives: I just don't log dives
    Location: Melbourne Australia and Willmar MN
    Every decade i buy new regs as manufacturing moves on .
    After successfully turning my brother in law to the Dark Side (diving) 8 am looking at new gear. But before i wander out and spend $1000+ on regs i have a question to the Dark Masters of diving( you guys) .
    Last saturday during a shore dive I experienced my first ever issue with my Mk25/s600/r380 setup after 10 years. ( yes i got them regularily serviced )

    Dive started normally - 2500psi fill - no issues. 30 min later @20ft i noticed the contents gauge was dropping visibly with every breath , then rebounding back to its actual pressure. Yes warning bells were ringing..... Below 1000psi the dive became impossible unless you liked 1/2 breaths. Back at 12ft i wasnt worried. Sitting at 12ft i removed my tank/BC much to the horror of my Freshly minted PADI open water partner.
    I noticed the first stage main spring opening violently with inhalations - looked normal - but just no flow . (please note i did have perfectly working5lt pony with me). Small slow bubbles were escaping from the first stage from the spring area.
    The regs did the same on the surface later -short stroking.
    Afterwards during cleanup at home i tried them without getting the problem .
    I did notice the regs now slowly degass for about 10seconds after taking them off the tank.
    Back for a service i know - but what is the first stage doing wrong?
  2. ddown

    ddown Barracuda

    # of Dives: 500 - 999
    Location: Morrice, MI
    Sounds like the valve on the tank wasn't open all the way
  3. ffdiver

    ffdiver Dive Shop

    # of Dives: 500 - 999
    Location: New York
    Same thing happened to me on my first wreck dive at 110ft. Turns out the DM who was helping me get into my rig, checked my air but turned the valve the wrong way. As I was down on the wreck, with every breath, my needle shot down to almost zero. As a new diver I was terrified and almost panicked.

    Lesson learned, always open the valve completely. Before you go into the water, test your regs and always watch the gauge as you take at least a few breaths of air. If the dial moves, your valve is not open all the way.

  4. halocline

    halocline Solo Diver

    What do you mean "manufacturing moves on"?

    The bubbles are probably from the little o-ring that seals the 2 piece (composite) piston together. (I think that o-ring leaks into the ambient chamber) There are two other spots that could leak air into the ambient chamber, the HP piston o-ring and the piston head o-ring. Any leak I've ever seen at the HP o-ring is pretty strong, never small slow bubbles. There's a back up ring on the piston head, usually they don't leak there.

    The 'degassing' sounds like IP slowly escaping which could also be IP leaking through the same spot in the piston where the two pieces join. That's not a user-serviceable spot, BTW, it means new piston. But what doesn't make sense to me is how the IP isn't just escaping out like normal when you purge the reg before removing it from the tank. Another thing that sounds strange is your description of watching the 1st stage spring....first of all, you can't really see it unless you're looking directly in the ambient chamber holes, and it hardly moves, although I guess if there was a supply air blockage and you sucked hard on the 1st stage, the IP would really plummet and the piston would more further off the seat.

    I agree that your breathing problem is a classic tank valve mostly closed issue and is probably unrelated to the bubbling. You could also have a lot of crap clogging the filter or dip tube.

    Anyhow, bring it back, if they can't figure it out have them try a different piston and see if that fixes it. Let us know, I'm curious about this one. They could start with just re-doing the HP and piston head o-rings, if that doesn't make a difference it's likely the piston internal o-ring.
    axxel57, cbrich and James R like this.
  5. elan

    elan DIR Practitioner

    # of Dives: 200 - 499
    Location: Toronto, Ontario, Canada
    As previously mentioned, tank valve was not open completely, clogged dip tube, valve or filter , try it with another tank.

    Bubble could be just trapped air unless they come non-stop, then I cannot give more options than halocline

    Dropping SPG needle suggest that at least the LP path in the reg is clean enough to provide air, the restriction is somewhere before the HP chamber.

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