MK10 leaks

[James79]

Yeah, so I get it. The regs were new to me but obviously used.

The DGX reg I mentioned in the last post is was purchased brand new and just developed the same leak... I'll send it to DGX for service.

If I find nicks inside the Mk10 body, is it pretty much game over for that reg?

Depending on where and how deep. If there's tiny scratches in the piston cap where the piston head rides, micromesh (super fine sanding cloth) can probably polish it out. In theory the same could be done with the HP o-ring land, but it would take creativity to get to it. Scratches on the piston shaft where it rides in the HP o-ring could be polished out as well.

Respectfully,

James

 

[Angelo Farina]

I am hunting down a small air leak in a freshly rebuilt MK10.
This was a fully rebuild reg. New o-rings, seat, etc. Ideas?

Did you rebuild the reg yourself, or was the job done by a shop?
Was a proper bullet-shaped adaptor used when inserting the piston in the reg?

 

[mr_v]

Did you rebuild the reg yourself, or was the job done by a shop?
Was a proper bullet-shaped adaptor used when inserting the piston in the reg?

Yes, I rebuilt it. The MK10 was an eBay find and proper tools were used to insert the o-rings. IP, and in-water tests did not reveal any issues shortly after the rebuild. In retrospect, I should have tested the regs prior to disassembly.

DGX was brand new in Feb '23.

Both regs did not leak at the beginning of the week. I inspected them for leaks as I dropped them off in water. The leaks became apparent only on the last day. It is possible that I could have overlooked, but the bottles were in clear water and usually I look at the regs for about ~1 minute to ensure no leaks.

 

[rhwestfall]

So, how did you extract the Piston stem HP o-ring? What did you use? What technique did you use to grab and remove it?

 

[ScubaBunga]

Yes, I rebuilt it. The MK10 was an eBay find and proper tools were used to insert the o-rings. IP, and in-water tests did not reveal any issues shortly after the rebuild. In retrospect, I should have tested the regs prior to disassembly.

DGX was brand new in Feb '23.

Both regs did not leak at the beginning of the week. I inspected them for leaks as I dropped them off in water. The leaks became apparent only on the last day. It is possible that I could have overlooked, but the bottles were in clear water and usually I look at the regs for about ~1 minute to ensure no leaks.

I always pre-check the used stuff just to see. I've gotten pressure gauges with swivels without o-rings at all and an MK10 that leaked horribly - took it apart and the orings just dissolved. But even those that were solid got rebuilt with new orings - always.
Hopefully the issue is a nicked o-ring or dirt and is an easy fix.

 

[Nemrod]

Depending on where and how deep. If there's tiny scratches in the piston cap where the piston head rides, micromesh (super fine sanding cloth) can probably polish it out. In theory the same could be done with the HP o-ring land, but it would take creativity to get to it. Scratches on the piston shaft where it rides in the HP o-ring could be polished out as well.

Respectfully,

James

I have taken a gun cleaning patch holder for .17 caliber and then taken a tiny piece of grey Scotchbrite threaded through and secured with a drop of Super Glue. Then using a cut off .17 caliber rod chucked in my drill and spun it inside the O-ring groove bore. If the scratch is just a burr in the chrome it may polish out. If the scratch is through the chrome and into the brass, say goodbye, it will never stop leaking. The piston head O-ring to the barrel is much lower pressure delta and minor defects there often can be dressed out. If there are deep scratches, pitting corroison or peeling chrome, not so good prognosis. The air can pass under the peeling chrome, peel that piece off and the air just finds another way under the chrome plating.

I sure wish I had a titanium (NIB) Mark 25, I have a NIB Kraken for trade, maybe, maybe not, lol! No peeling and pitting chrome there.

I try not to use anything more than a hard, sharp pointed plastic pick to get that O-ring out, it can be a chore sometimes.

 

[mr_v]

Ok, so problem fixed.

I opened MK10, replaced the stem o-ring, closed it up. Initial tests showed IP creep. Opened it up again, and, as suggested in a separate thread, wiped the piston knife edge and the HP seat with lint-free qtip. Subsequent tests revealed no bubbles and no IP creep. Tested charged with the tank off in water for a few. hours and I was satisfied with the outcome. I have no idea what caused the problem, but seems like we are good to go now.

The second reg, DGX XTRA, was replaced by DGX.

@rhwestfall - I use several approaches to remove the stem o-ring. I prefer using a brass o-ring pick. If it does not work, then the steel double hook pick. In each case I use the MK10 o-ring kit to push the ring out. Also, lots of wood dovels of different sizes.