Scubapro MK2 leaking yoke retainer

[BenjaminF]

I was recently given a Scubapro mk2 because the owner wasn't using it and the yoke retainer leaks a steady stream of small bubbles.
The pressure on the LP ports is stable and it breaths well (in a shop lab and a pool), but somewhere between the the yoke retainer, the o-ring inside of it and the yoke body, something seems to not be sealing.

Could it simply be that the o-ring needs to be replaced? If so, could somebody perhaps give me a pointer to something which lists the size of the o-ring?
What other directions could I look in for the root of the problem?

 

[Fishpie]

Have you undone the yoke nut yet?
Was it loose?
It has a fixed static o ring that rarely needs replacing.
1st thing I'd suggest is you remove the nut, examine the o ring, turn it over and then put everything back together and see if you still have a leak.

 

[BenjaminF]

I have tried that. I regreased the o-ring before putting it back onto the nut, but the leak is still there.

 

[Fishpie]

Just checking.......are you sure it's not the tank o ring?

 

[BenjaminF]

Fairly certain, but I'll check again on Tuesday just in case.
After greasing the o-ring, the amount of air leaking DID go down, so it seems to have helped a bit. This is why I thought that maybe it's just a problem with the o-ring and it needs to be replaced, but I can't find a size for it.

 

[redacted]

I'm pretty sure it is a 015.

Which means I have it wrong in this thread: http://www.scubaboard.com/forums/repairing-your-own-gear/322518-scubapro-o-ring-sizes.html

I would not expect lubing to stop such a leak. If it is that o-ring, then either the o-ring is bad or one of the sealing surfaces. I would still look at the tank yoke o-ring or retainer sealing surface on the tank yoke as the prime suspects. If you twist the 1st stage while it is leaking, does that effect the leak? If it does, I see that as evidence of the problem being in the tank yoke seal.

 

[BenjaminF]

I did try twisting the 1st stage, but that had no effect on the leak.
In that thread, Zung has added MK2+ as a note in his post (and spreadsheet), but doesn't say where in the 1st stage it is. Thanks. I'll start asking around for one of them at the local shop when it opens on Tuesday and see if swapping it helps.
Could it be the actual metal surfaces which are the problem?

 

[redacted]

Could it be the actual metal surfaces which are the problem?

Yes. Deposits, corrosion, or dings and scratches on metal sealing surfaces may result in leaks. They are usually fairly easy to feel or to see with nake eye or with magnifying glass. But the same is true for defective o-rings.

 

[BenjaminF]

Ok. Thank you. I'll check for those too.

 

[halocline]

I've seen a few yoke retainer o-rings leak, usually it's because someone loosened the retainer by grabbing the reg while it was on a tank and twisting. Then the o-ring gets extruded and nicked. It seems less likely that it would happen on a MK2, but you never know. Try a new o-ring, see if that helps. It is listed as a 015.