MK10 leaks

[mr_v]

Howdy,

I am hunting down a small air leak in a freshly rebuilt MK10. The leak barely adds up to a few bars an hour when tested as follows:

- Charge the reg
- Close the valve all the way
- Observe a slight pressure drop and tiny - very tiny bubbles every 5 seconds

The bubbles are coming out of the holes as indicated below:

This was a fully rebuild reg. New o-rings, seat, etc. Ideas?

Thank you!

 

[Kupu]

The piston stem oring is possibly the cause of the leak, or the piston head oring.
I would switch them both since the reg is coming apart, using a piston bullet to protect the 85-90 duro piston stem oring.

 

[barth]

I guess it leaks at the piston head o-ring or piston stem o-ring.

Take a closer look and try to find the source of the leakage . Examine metal and o-ring surfaces for any signs of dirt or scratches.

 

[James79]

Only two ways air gets to the ambient chamber like that. Either high pressure getting past the Piston stamo ring, or intermediate pressure getting past the Piston head o ring. My first suspicion would be a minute scratch on the ceiling surface that the Piston head rides in.

 

[rhwestfall]

freshly serviced trashed....

(though the hope is that they didn't use a bullet, and nicked the stem o-ring...)

 

[p_kos]

If you lay the reg on its side underwater you may be able to tell which side of the hole the bubbles come from. If it’s from the side towards the SPG it’s probably the piston stem oring. If it’s from the side towards the hoses it’s probably the piston head oring. That said, it’s probably not the oring but a scratch in the land where it sits.

 

[mr_v]

Will do a few more tests. Interesting that you've mentioned dirt. Another regulator - DGX XTRA - that hasn't been service yet developed the same problem. I was in an environment where the regs got exposed to some fine sand/dust, not sure if any fine particles got in...

 

[Nemrod]

As stated, the leak will either come from the piston to body O-ring or from the piston stem where it goes through the body to the HP side. More than likely the O-ring groove that is inside the body where the piston stem passes through was scratched by use of a dental pick to extract the O-ring. The other possibility is that the piston stem/knife edge was shoved through nicking the O-ring.

 

[mr_v]

As stated, the leak will either come from the piston to body O-ring or from the piston stem where it goes through the body to the HP side. More than likely the O-ring groove that is inside the body where the piston stem passes through was scratched by use of a dental pick to extract the O-ring. The other possibility is that the piston stem/knife edge was shoved through nicking the O-ring.

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?

 

[Nemrod]

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

Unfortunately many a regulator has been ruined by scratching the sealing surfaces with a steel dental pick when removing that O-ring that resides up inside.