MK17 Scratching my Head on this one.

[Scubadude_LA]

Have a Mk17 first about 3yrs old. Light use so far. Problem developed where it would be mounted on a tank and when pressurized would free flow from the bleed hole on the tank valve and I would have to cycle the tank valve a few times to get a seal. When time to remove the mk17 from the tank it was extremely hard to unscrew, usually dislodging the tank oring in the process. I noticed that when finally getting it loose a small amount of pressure is still left on the HP side after fully purging the seconds.
I did not do a full kit replacement, only a full breakdown, cleaning and reassembly. Parts looked good and clean by eye (reg is a dedicated singles kit and rarely used). Put it back together. same results, Filter seems clean and ok.
Before I do a full breakdown and new kit, any ideas? Spring??
thx

 

[parzdiver]

Is this DIN or yoke? Does this happen with multiple tanks or just one tank?

 

[axxel57]

http://www.scubaboard.com/forums/regulators/485257-trouble-removing-yoke-after-dive.html

 

[underH2Oman]

My guess is the tank o-ring needs replaced as it is not sealing properly and if air leaks behind the o-ring it can hold pressure behind it and make it hard to get the yolk off or DIN unscrewed. It may even pop the o-ring out when you remove the regulator.

 

[halocline]

Have a Mk17 first about 3yrs old. Light use so far. Problem developed where it would be mounted on a tank and when pressurized would free flow from the bleed hole on the tank valve and I would have to cycle the tank valve a few times to get a seal. When time to remove the mk17 from the tank it was extremely hard to unscrew, usually dislodging the tank oring in the process. I noticed that when finally getting it loose a small amount of pressure is still left on the HP side after fully purging the seconds.
I did not do a full kit replacement, only a full breakdown, cleaning and reassembly. Parts looked good and clean by eye (reg is a dedicated singles kit and rarely used). Put it back together. same results, Filter seems clean and ok.
Before I do a full breakdown and new kit, any ideas? Spring??
thx

It's probably pressure building up behind the tank o-ring. Try replacing that o-ring, and make sure the reg fits really perfectly on the tank valve mating surface before tightening it up. I suspect this has almost nothing to do with the regulator itself. But, you should inspect the flange on the first stage that mates with the tank valve and make sure there are no imperfections on that flange. Same thing with the o-ring channel on the tank valve.

Ever seen anyone pop out a tank valve o-ring with air pressure? They do it by loosely connecting the regulator (so that it doesn't trap the o-ring firmly in it's groove), cracking the tank valve, and hoping that the burst of air will push the o-ring out of it's groove. I suspect a similar sort of thing is happening with your tank.

 

[Scubadude_LA]

This is a DIN version.
Tank O-ring has been replaced more than once to troubleshoot.
Happens on every tank that it is connected to.
When connecting I thread up the reg, then just before it gets tight I do take extra precaution to make sure things are squared up while sealing it up, I always do that to ensure a good seal.

What has me thinking there is some issue in the reg is the fact that after purging the seconds fully there is still residual pressure left on the HP side of the orifice, not much. But, it doesn't take much there to make a reg hard to loosen.

I will reinspect the flange, oring groove, etc and see what I can come up with.
Thanks for the replies.

Edit: All my tanks have modern Thermo valves.

 

[underH2Oman]

Are you using the correct o-ring size? Try using the white one supplied by Scubapro. I have had some o-rings that were used in the DIN end fall out when used but when used the one supplied from Scubapro never an issue.

 

[redacted]

This is a DIN version.
Tank O-ring has been replaced more than once to troubleshoot.
Happens on every tank that it is connected to.
When connecting I thread up the reg, then just before it gets tight I do take extra precaution to make sure things are squared up while sealing it up, I always do that to ensure a good seal.

What has me thinking there is some issue in the reg is the fact that after purging the seconds fully there is still residual pressure left on the HP side of the orifice, not much. But, it doesn't take much there to make a reg hard to loosen.

I will reinspect the flange, oring groove, etc and see what I can come up with.
Thanks for the replies.

Edit: All my tanks have modern Thermo valves.

Some SPGs and HP hoses can be very slow bleeding off pressure which can cause this problem. Test by removing HP hose and install a port plug.

 

[halocline]

This is a DIN version.
Tank O-ring has been replaced more than once to troubleshoot.

Sorry, when you started talking about the tank o-ring I assumed you meant yoke. Try awap's suggestion about replacing the SPG with a port plug, hopefully that will give you an idea. The only thing I could think of would be some sort of restriction in the tiny HP orifice to the SPG port that was slowing the flow of HP air back into the regulator when you purge. That's a long shot.

 

[axxel57]

Which 2nd stage are you using?

Are you sure that the purge button can be pressed deep enough to empty the system completely?

With SP 2nds it should not be a problem, with other brands it might be.

Otherwise check as said the SPG.