Stuck MK10 Piston cap (Scubapro)

[halocline]

A couple of tips about putting it back together. 1) You really need to find a new HP o-ring. You almost certainly damaged the old one taking it out. I deliberately damage them during removal; I bury the tip of the double hook o-ring pick in the o-ring, that way I know it is not scratching the journal where that o-ring sits. A standard o-ring pick is not a great tool for removing that o-ring. 2) If you don't have the piston bullet tool, you'll need to find something that will function as one, otherwise you'll tear up the o-ring with the piston edge when you install the piston. 3) If you re-install the same seat and do not flip it, you'll likely get some IP creep as the piston cuts a new groove in a slightly different place, intersecting with the old groove.

The fact that you're talking about a flat seat probably means this reg has not been rebuilt in a loooooonnnng time. That might help to explain the difficulty getting it apart. Anyhow, the new seats with the conical seating surface are much better, so I'd just leave it apart until you get a kit that has one of those. Actually, it will have three.

I assume you're in the military; not too many english-writing-scuba-enthusiasts would otherwise be living in your locale! If by some chance you know anyone from a San Antonio base that's heading your way I'd be happy to send you a seat and some o-rings.

 

[DA Aquamaster]

I had an adjustment knob badly stuck in a G250 air barrel once. Nothing I tried got it unstuck and eventually the shaft of the knob snapped. Since it was a customer reg and time as an element I just ordered a new air barrel and knob (not horribly expensive in the pre-G250V era, but oddly enough they are now a lot more expensive). For kicks I liberally WD-40'd the stuck parts and let it sit checking it every week or so. It took about 6 months but the knob eventually took me by surprise, loosened and screwed out with finger pressure.
So I order a new adjustment knob for it and upgraded a G200 to a G250.

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Be extremly careful in removing the HP piston stem o-ring that you do not scratch the groove inside the reglator body. It's the fasted way I know to turn a Mk 10 into a paperweight. As indicated above, stabbing the o-ring is a good practice if you are using a steel o-ring pick. Generally speaking I only use brass picks in that area. Parker Seal sells a very nice brass two pick set through scubatools and it works very well. The second pick has a flat rounded end and an inverted V end. That pick works great to both start the o-ring into the groove inside the reg body and then to press it into place (while holding the edge you started in place with a pointy o-ring pick). That works a lot better in my opinion and is much faster than using the Scubatools Mk 10 in stallation tool.

There were a couple of transitional styles of seats between the old flat white nylon seats and the current grey seats and you'll find transitional concave seats in a few different colors and materials. The older flat seats are the only seats that can be flipped.

The small hole in the back is intended to be used to blow the seat out with air pressure. A rubber tipped blow gun attachment works fine. I have however also just held the retainer tightly against a yoke scuba valve using the valve o-ring and hand pressure to create the seal. Crack the valve slowly and it will normally pop right out unless it is badly stuck.

If it's been awhile since the reg has been serviced you will want to replace all the o-rings and in particular the swivel seat o-ring.

If you are militarty and deployed to the sand box, send me your APO address and I'll send you a MK 10 annual service kit , the extra o-rings you'll need, and enough Christolube to do the job.

You'll also definitely want a piston bullet to install the piston, as the sharp edge on the piston can cut the o-ring.

 

[ams511]

There is nothing wrong with the hot water/freezer thing, but it is only partially working the problem which is salt and or corrosion rather than it just being too tight.

Assuming we don't care about the reusing the seat and orings, how hot can you go? For example can you submerge it in boiling water (not still on the stove) and then drop it in an ice bath?

 

[DA Aquamaster]

The heat difference between boiling water and ice isn't going to warp anything, so go as hot as you want.

Just remember the idea is to get the outer piece (the swivel cap) to expand (with heat) while the iunner piece (the regulator body remains contracted because it is cold.

With that in mind, you need to put it in the freezer first to cold soak the whole thing. then place just the turret/swivel cap end of the stage in the boiling water up to a point just short of the threads. Then (insert lots and lots of hope and luck here) the heat will transfer to the outer portion of the threads on the cap and expand them at the connection while the threads on the reg body remain cold and contracted, creating more clearance between the threads. Of course the problem is that heat transfer occurs across the threaded connection mitigating the desired effect.

And again, I don't think that does much to treat the basic problem - salt deposits and corrosion. So when it does not work, just leave the whole reg (properly sealed of course with a o-ring sealed inlet cap and all the LP and HP ports selaed with port plugs) in the boiling water for 10 minutes or so and let the hot water itself work on the salt deposits.

 

[Manow]

Thanks to everyone for the help! Yes, I have a Piston Bullet, cristo lube (2 oz tube) and about another $250.00 invested in Scubatools.com., plus an inch-pound torque wrench I bought off ebay. I actually bought the brass pick kit, and I bent the hook into a shape that allowed careful removal of the tiny o-ring that the piston passes through. The MK10 I'm working on was a $30.00 ebay special, and it had some old blue colored hoses attached to it. I suspect it was stored in a garage or storage locker for a long time. It actually looks really good now. The HP Seat does have a bowl type mark in the center. Yes, I'm going to replace EVERYTHING inside the MK10. I'm off to Thailand next month for 2-weeks of diving & R&R. I also have a few friends there that I hope can hook me up with rebuild kits for the MK10, the MK5, MK2 and my newest MK25. I use the MK25 as my main rig, and the MK2 as a back-up. I don't want to wrench on them until I have a good feel for what I'm doing, and I'm some place I can test my work. Vance's book, the tools, the MK10, MK5 and a pair of 108s are my training aids. (I have a lot of free time) Again, I won't take my "good" gear apart until I learn a little more. The MK5 is pretty much out of play because I can't get the drive extension through the tiny yoke hole, and the thin yoke really isn't something I want to deal with right now anyway. Nonetheless, I'll keep it around because I will eventually figure out a way to remove the yoke. I pulled it apart, less the yoke. It looks okay inside, and I noted the piston is much larger than the MK10's. The thin yoke is a concern, and until I have better understanding of the risks, I'll set it aside. Yes, I'm still looking for a clean 109, but they arn't cheap. I've been staring at the New Scubapro 700A. Not sure the 700 is worth the money (Leisure Pro has it paired with MK25 for about $600) The fact that it is brass has a certain coolness factor; just don't know if it's worth the money for the bling. Some of the pieces inside my 108s are in poor condition, and I hope I can find parts for these in Thailand. Sorry if I've gone on and on; hey I'm new at this. Thank you again to everyone, and your comments, and cautions are taken seriously. Thanks again. P.S., if I stike out in Thailand (on the parts; not the women), I might take you guys up on the offer for the HP Seat and O-rings, but I insist on paying you for the gear. Thanks again.

 

[Zung]

Your MK5 might not be dead yet: removing the yoke retainer is easy, just clamp the bolt in a vise and turn the body. Then look for a 3000 PSI yoke; if it fits the retainer, you'll have yet another reg to play with.

Because reg's are life support equipment, the minimun number of reg's per diver should be 4, at least; double redundancy, you know.

 

[DA Aquamaster]

Since I use Mk 10s and Mk 9s for stage and deco regs that I have converted to DIN, I have a whole box full of Mk 5/Mk 10 3000 PSI, 9/16" yokes with no real future use in sight. I have several of the original flat yoke screws and may have one or two of the newer round yoke knobs sitting around as well.

 

[ams511]

(Leisure Pro has it paired with MK25 for about $600).

I am not sure what the deal is with Leisure Pro anymore. They dramatically increased their price on Scubapro items. Some items have been more than doubled in price.

 

[ams511]

And again, I don't think that does much to treat the basic problem - salt deposits and corrosion. So when it does not work, just leave the whole reg (properly sealed of course with a o-ring sealed inlet cap and all the LP and HP ports selaed with port plugs) in the boiling water for 10 minutes or so and let the hot water itself work on the salt deposits.

I am glad you mentioned that. I would have left the reg open thinking it could not hurt because I am going to rebuild it anyway.

 

[DA Aquamaster]

I am glad you mentioned that. I would have left the reg open thinking it could not hurt because I am going to rebuild it anyway.

It won't hurt to get the reg wet inside - as long as you actually get it open in a timely manner to clean it and dry it. The problem occurs if you are not successful and walk off for a week or two...