How To Service Mk15

[oceancurrent]

I have worked on a number of ScubaPro regs, but this is the first time I am encountering an MK15. This one is pretty badly corroded on the inside due to salt water intrusion, it seems. So I am taking it all apart for cleaning. With some struggle I managed to get most of the body apart, but getting the piston stem O-ring and washers out is seemingly impossible. There is a retainer holding the o-ring and washers in place - managed to get it out with a lot of difficulty, but still nothing comes off. There is also a washer stuck on the opposite side of the piston shaft which I can't get off. I am either doing something completely wrong or this first stage is unbelievably unfriendly for servicing - no wonder it is an oddball reg in the ScubaPro line. I tried to look for the service manual, but all I found is the schematic, which is of little help. Does anyone have a copy of the service manual for this reg or know the procedure for removing the parts from the piston shaft in a non-destructive way (hopefully reusing them) by any chance?

 

[redacted]

PM Halocline if he does not show up soon. He has a Mk15 he has serviced. I have never messed with one but do recall that the inner nylon washer is pressed into place and should not be removed. Sounds like yours needs a good US cleaning.

 

[oceancurrent]

Thank you, awap. Ah, that explains why I can't budge the washer. So, I will leave it alone and just polish it a bit. Hopefully, its only function is to reduce the friction of the piston against the shaft (I don't see what else it is there for).

Now the question is - what is a reasonable way to remove the stem shaft oring without damaging it or the washers around it.

 

[halocline]

There are two nylon washers, one on the ambient chamber side of the body, one on the HP side. Only the one on the HP side comes out. You'd think they would have made this more clear in the schematic. It's been a while since I serviced my MK15 (over 5 years, and I still am waiting for any sign of creep or problem) but my memory is that the nylon washer goes in first, then the o-ring, then another plastic washer that I think is brown. The whole arrangement is held in place with a circlip which takes some really skinny circlip pliers to remove. Scubatools has those pliers if you need them.

So once you get the circlip out, pull out the brown plastic washer, then look closely to see if you're looking at an o-ring or a nylon washer. If it's an o-ring, pull it out, then carefully pull out the nylon washer, then you're done. If the washer is 'outboard' of the o-ring, take them both out but don't touch the washer that's visible from the ambient side.

You'll need a good o-ring pick to get the old washer out, I like those double hook o-ring picks from scubatools. They have a right shape to extract stubborn washers without without scratching the regulator body.

 

[oceancurrent]

Thank you very much, halocline. Indeed, the washer and plastic pad sandwiching the oring were stubborn. But I was more insistent with the pick, now that I got a confirmation from you that they are removable, and they finally came off. Cleaned everything up well, lubed, and put it back together. Works great and locks the IP solid no creep or leaks.

My overall impression of this reg is that it is very unfriendly to service. I'd choose MK5, 10, or 20/25 any day over it.

 

[halocline]

Actually if you have the right circlip pliers it's as easy to service as any of the other SP balanced pistons, and it does have the advantage of the bushing system for minimizing HP o-ring extrusion. I really like my MK15 and have considered finding another one to replace my MK10 doubles set up. I think the MK15 can go longer between rebuilds than the MK10, and it's better for HP tanks. The only issue with the MK15 is finding seats, as they are unique to that model.

My favorite is still the MK5, but I would not disparage the MK15 at all.