MK25/G260 whistling

[buddhasummer]

I recently bought the above regs and have used them a handful of times. Today noticed a whistling sound on inhalation. Can someone please tell me what it could be and how to fix it. I had the same issue with a Z2 a couple of years back but returned it to get fixed. This one is problematic to return and assuming a simple fix I'll do it myself. Is it likely to be a lubing issue or the spring. TIA. Cheers.

 

[lowviz]

Whistling underwater or dry?

 

[tstormdiver]

Typically in the 1st stage. Usually insufficient lubrication between the piston stem & the stem O-ring. Irritating, yes, not particularly dangerous. Basically, 1st stage would have to be completely disassembled & re-assembled using the proper amount of lube & a stem O-ring insertion tool (a "brass bullet" for the piston also helps to prevent cutting the O-ring as the piston is pushed through.

 

[buddhasummer]

Whistling underwater or dry?

wet...

---------- Post added July 20th, 2015 at 01:56 AM ----------

Typically in the 1st stage. Usually insufficient lubrication between the piston stem & the stem O-ring. Irritating, yes, not particularly dangerous. Basically, 1st stage would have to be completely disassembled & re-assembled using the proper amount of lube & a stem O-ring insertion tool (a "brass bullet" for the piston also helps to prevent cutting the O-ring as the piston is pushed through.

yes, no noticeable drop in performance but irritating as hell. Piston regs eh, I'm now two for two, I've had the same issue with both piston regs I've owned from new. Seems a bit iffy to me. Is this a common occurance with piston regs?

---------- Post added July 20th, 2015 at 01:58 AM ----------

How often is this likely to occur? Is it a regular thing that needs addressing on a regular basis? Or just if the issue is present from new?

---------- Post added July 20th, 2015 at 02:06 AM ----------

I'm in the process of ordering tools. Will it be ok for a few weeks or does it need urgent attention? Can I dissasemble and reassemble using same parts? Thanks.

---------- Post added July 20th, 2015 at 03:54 AM ----------

The part numbers or the culprits so I can identify them on a schematic would also be helpful, thanks.

 

[tstormdiver]

yes, no noticeable drop in performance but irritating as hell. Piston regs eh, I'm now two for two, I've had the same issue with both piston regs I've owned from new. Seems a bit iffy to me. Is this a common occurance with piston regs?

I have only had Piston 1st stages (MK25's), so I don't have much to compare to. My recreational reg is beginning to squeak some,... but it has not been serviced for about 3 yrs. I am sure the lubrication is getting quite thin. All my other 10 MK25's are doing fine.

How often is this likely to occur? Is it a regular thing that needs addressing on a regular basis? Or just if the issue is present from new?

Basically it really depends on how well it is lubricated. By the training I received from ScubaPro, when assembling the stem O-ring & rings, there is a generous layer of grease between each layer. Your issue may have come from the factory, but I have seen it develop after routine servicing. All depends on the proper amount of lube.

I'm in the process of ordering tools. Will it be ok for a few weeks or does it need urgent attention? Can I dissasemble and reassemble using same parts? Thanks.

If general lubrication is the issue & performance is not compromised, other than the squealing grating on the nerves, there should be no real issue. If it is a problem with the stem O-ring, it should be noticeable by an IP creep. I am not going to say whether you can or can not reuse parts.... but I do know the parts can be difficult to get. If anything may need to be replaced, it would be the stem O-ring. It is possible (unlikely) the whistle may even be from a microscopic nick in the O-ring.

 

[buddhasummer]

Thanks Tammy. Being that the reg is new I'm going to assume it came from the factory like that. I can get the service kits no problem. I'll contact the shop I bought them from and see what they suggest. I'm happy to take it apart and fix it myself as long as it's not going to cost me any money lol. I could ship it back to the shop I bought it from but that's going to take a while as they take long vacations over summer. It sounds like it would be prudent to have a service kit on hand in case O rings need replacing. Does the "stem" go by another name as I have a schematic but cannot find "stem". It's funny I've owned diaphragm regs all my diving life and never had a single issue, but have had problems with the only two piston regs I bought from new, statistically improbable I would have thought. Just unlucky I guess.

---------- Post added July 20th, 2015 at 07:13 AM ----------

There is no ip creep so will guess you're on the money re lubrication.

 

[redacted]

The Mk25 piston does not have a sharp knife edge, so a bullet tool is not required to protect the piston HP o-ring. But there is a pair of bushings sandwiching that o-ring that can be dislodged if the special assembly tool is not used to hold them in place as the piston is inserted. If you do screw it up, it will let you know very clearly when you put it under pressure.

You could try leaving the HP seat retainer in place and simply removing the ambient chamber from the body while holding the piston in place. This can be accomplished by using air pressure or a tool through the end LP port as you separate the ambient chamber from the piston head. Then lube the hell out of the piston shaft pushing the lube down between the body and the piston shaft. Excess lube will not be a problem with this technique so have at it.

Good luck.

 

[buddhasummer]

Thank you. Lube the hell out of it I will.

 

[Nemrod]

Yes, piston first stages are known to whistle, it is a common problem with them. Sometimes they stop, sometimes get worse. Lubricate the piston shaft, install a new seat or flip it, rotate the spring and lube the end sufaces or place a thin mylar shim on the end of the spring. Change the IP up or down slightly.

N

 

[buddhasummer]

Yes, piston first stages are known to whistle, it is a common problem with them. Sometimes they stop, sometimes get worse. Lubricate the piston shaft, install a new seat or flip it, rotate the spring and lube the end sufaces or place a thin mylar shim on the end of the spring. Change the IP up or down slightly.

N

Thanks James. Wish I'd known this about piston regs before I bought it, seems a lot of messing around. If I live long enough perhaps my hearing will decline as my eyes have done then the noise will not bother me so much. By the hour mark I ended my dive as the whistling noise was doing my head in, like some sort of aural Chinese water torture.