MK 25 service of seat o-rings.

[halocline]

You might as well disassemble the MK25, pull the piston out, then as Zung said you can push out the o-ring and bushings, replace the o-ring and hope it fixes it. You could get the installation tool, or you can try the old way of putting everything in place without the piston, including the seat assembly, then the idea is that the seat and spring hold the bushings and o-ring in place while you install the piston. I've done that in a pinch on a few MK20s with success in the past, but I wouldn't recommend it as a general practice. The bushing installation tool is pretty useful if you can find one. Or, you can try Zung's approach of putting the piston in place and then pushing the bushings and o-ring over the piston shaft, then install the seat retainer.

Something's not installed correctly, or was damaged in installation, that's the only reason I think of for an actual leak at the HP o-ring. The common problem is the squeal/honk during breathing, but no leak; that's a kind of resonance with the piston/main spring that's not dampened by sufficient lube.

Unless you want to go back to the tech, tell him to try again.

 

[divingtactics]

As previously mentioned, a leak from the ambient pressure chamber is usually, the 010 o-ring, part 22 in the previous diagram. If you don't use an 85 or 90 duro o-ring and substitute it for a softer 70 duro o-ring, it will A) Leak or B) Not last very long.

A friend of mine recently rang me with this exact problem and after taking it back to his service tech twice to no avail, he bought it over to my place and I simply replaced the 010 with a harder o-ring. His service tech never put the proper harder o-ring in place and when he was asked to look at the problem a second time, he only removed the HP seat and checked that and the 011 on the seat. I was flabbergasted but not surprised and this is the reason I service all my own regs now. Look to the HP stem seat o-ring, this will be where your issue lies. Halocline's advice has been spot on.

 

[ams511]

What is the DIY scene like in Australia? In the US it is sad with the manufacturers hoarding knowledge.

 

[divingtactics]

What is the DIY scene like in Australia? In the US it is sad with the manufacturers hoarding knowledge.

It is much the same here with difficult access to parts kits and knowledge for non manufacturer trained folks, but Frogkick offers all the manuals and I'm able to buy parts kits online. The only thing I haven't been able to find is a good source for the latest technical updates for Apeks and Scubapro.

 

[triggerman365]

Well, the mystery is solved. Today I bought a MK 25 service kit and tore down my MK25. What I found was that the SP Tech who serviced my reg had used the wrong o-ring (part 24 on the schematic). I put the proper o-ring in, put it back together and the IP is locking up at 137! It look to me like the SP Tech incorrectly used one of the 01-050-138 o-rings instead of the 01-050-136.





By the way, for any one thinking of servicing a MK25, it is a piece of cake, easier than a MK5 or MK10.

 

[Zung]

Glad to hear about:

1. The happy ending
2. Yet another proof of the value of "professional service"
3. The ease of service of the MK20/25 vs MK5/10: I'm totally with you, I love it when everything just drop right in, no cursing required, but I got constantly kicked whenever I raise this topic with the resident gurus.

 

[redacted]

Glad to hear about:

1. The happy ending
2. Yet another proof of the value of "professional service"
3. The ease of service of the MK20/25 vs MK5/10: I'm totally with you, I love it when everything just drop right in, no cursing required, but I got constantly kicked whenever I raise this topic with the resident gurus.

It is not that the Mk20/25 is hard to service compared to the Mk5/10. And, the time between service is quite good once you get rid of any brass pistons that are still around. My wife dives a Mk20 and I have one spare. My bitch with the Mk20/25 (and 10+) is the SP proprietary seat. I do not trust SP USA. And then there is the composite piston which will fail in time. Hopefully, when SP stops supporting that model, there will be plenty of parts in the scuba regulator junk yard that can be salvaged, if you can get seats.

 

[ams511]

It is not that the Mk20/25 is hard to service compared to the Mk5/10. And, the time between service is quite good once you get rid of any brass pistons that are still around. My wife dives a Mk20 and I have one spare. My bitch with the Mk20/25 (and 10+) is the SP proprietary seat. I do not trust SP USA. And then there is the composite piston which will fail in time. Hopefully, when SP stops supporting that model, there will be plenty of parts in the scuba regulator junk yard that can be salvaged, if you can get seats.

Maybe that is why they changed the free parts for life program. They may be expecting many replacements in the future.

 

[divingtactics]

Well, the mystery is solved. Today I bought a MK 25 service kit and tore down my MK25. What I found was that the SP Tech who serviced my reg had used the wrong o-ring (part 24 on the schematic). I put the proper o-ring in, put it back together and the IP is locking up at 137! It look to me like the SP Tech incorrectly used one of the 01-050-138 o-rings instead of the 01-050-136.


View attachment 155675


By the way, for any one thinking of servicing a MK25, it is a piece of cake, easier than a MK5 or MK10.

Good to hear you have it working as it should be now and it is great that you followed it up with the resolution, as most don't. It was the most likely thing to be at fault and unfortunately, I see this type of shoddy service from supposedly 'Qualified and Factory Trained' service techs all too often. I've seen wrong parts put in, parts missing, parts cut and put in, port plug hex nuts stripped, C-Spanner holes badly burred, spanner faces badly bruised - it just never ceases to amaze me.