Honking sound - extremely annoying! - Mares v16

[Lakerat789]

Mares v16 First stage with Orbiter Regulator/Nikos Octo.

It's developed an incredibly annoying honking sound when I breath in - took it to get looked at by my local dive shop in July following a series of dives and they couldn't replicate the issue. Just returned from 14 dives in MX, after 4 dives the problem returned and was so annoying after another 4 dives that I had to ditch it and use a rental instead.

I did however notice some consistencies and I'm hoping a guru might let me know what to ask to have checked specifically when I take it in for service. The honking sound on breathing was LOUD (loud enough to bother my fellow divers and be a source of entertainment on my gopro footage) and apparent with both the Regulator and then with the Octo (which I tried out of sheer frustration). Air delivery is ok, but you can feel the vibration in the hoses with the honking. The honking only started (and this was over several dives I noticed this) when I was below 60ft and when my tank pressure dropped to 1800psi and continued all the way down to 800-900psi. Equipment was 8 months into the yearly service and had approx 30 dives/use.

Any help greatly appreciated.
Rick

 

[halocline]

This is something I would associate with piston 1st stages. It's a harmonic resonance; as air rushes across the piston edge and flows into the piston, it causes vibrations just like a flute player blowing air across the mouthpiece of a flute. Basically your first stage has turned into a very bad flute. (Look on the bright side, even a bad flute is worth more than a regulator!) Then the piston vibrating gets the spring vibrating and that produces the honk. Since (I think) the mares 1st stage is a diaphragm, I'm not sure how it could be happening. Sorry I wish I could help you more.

This also happens with 2nd stage diaphragms, they can vibrate against the case and act like an expensive kazoo. But this usually disappears under water, and you said it did it with both primary and alternate 2nd stages. So it's a 1st stage issue. The fix is a rebuild.

 

[JackD342]

I have to wonder if there are some old or mismatched poppet valve parts in service inside the 1st stage. (I don't know if that would manifest itself as "honking," but it is worth a try.)

The V16 used the SCS poppet valve - neither part was replaced with annual overhauls, but that is a pretty hard working valve to rely on zero wear and tear over decades of use. Also, neither of the two parts is available now for replacement, but every time I see one come in I upgrade it to the current ACT valve.
Now, it is also possible that at some time in the past your V16 SCS valve was upgraded to the MR16 version of the valve, which does have the poppet replaced with service overhauls. (I know every time I see one of those old valves come through I automatically do the upgrade)
And if that SCS/MR upgrade was done long enough ago, then the earlier/older MR poppet seat should NOT be used with the current ACT poppet. That is easy enough to upgrade - Mares even has an ACT Upgrade Kit that includes a new spring along with the poppet and poppet seat to provide a nice fresh start.

Could be something else entirely, but you should ask your LDS just what valve is inside your 1st stage. Hopefully they made a note of it at the time, or the tech remembers working on your relatively rare V16.

 

[lowwall]

I had the same problem with my old Mares MR22 first stage on my recent Coz trip. It didn't happen every dive, but it was highly annoying when it did. For me it was right around 1200psi and I could actually stop it by reaching back and covering the nut at the top of the reg with my finger. Once I figured this out, I was doing this on every inhale until the tank pressure dropped enough for it to quit. Good thing I believe in long exhalations.

Luckily I never got down to 1200psi on my 2 cenote dives

I picked up a slightly less vintage Mares MR42 with my 2 Proton Metal seconds from a fellow scubaboarder before the trip. I'm going to try to find someone who really knows old Mares gear and get it serviced so I can swap it in before my next trip.

Edit - I think I may have found my guy one post up