replacing mk200 hp seat

[redacted]

FWIW, I used a MK15 for reg service practicing purposes and had symptoms similar to yours. awap diagnosed it correctly as piston o-ring leaking. In my case, the o-ring was the right size, just worn. Replacing it did the trick. The HP seat did cause an IP creep (you need an IP gauge to detect that), but replacing it with a new one solved the problem. I just pried it out (gently) with a brass pick. It's not gonna be reused to so scratching it further isn't an issue. However, be careful not to scratch the other parts of the reg.

Best way to remove the seat from the carrier on a Scubapro BP is to blow it out with an air tool.

 

[bada3003]

The seat on an unbalanced piston (MK2, MK200, MK3, AL Aquarius, etc.) is on the piston itself not on a carrier as on a balanced piston (MK5, 10, 15, 20, 21, 25). So the removal is different. You can also flip the seat on an unbalanced regulator.

Thanks, that's good to know.

---------- Post added May 19th, 2014 at 10:27 PM ----------

Best way to remove the seat from the carrier on a Scubapro BP is to blow it out with an air tool.

Will try that next time. Thanks.

 

[Six2Life]

Best way to remove the seat from the carrier on a Scubapro BP is to blow it out with an air tool.

I mount the 1st stage on a tank, turret down. After removing the seat retainer, I flip it and hold the flat side down against the open HP air chamber while covering the two pin spanner holes with my thumb and forefinger. Usually cracking the tank valve will pop the seat up into my hand. Probably not the safest, but it works well if you're lazy like me.

BTW, I have a pile of MK200 kits if the OP needs one. They are older with the PU orings, so those will likely need to be tossed, but the seat, filter, and star retainer should be GTG.

 

[runsongas]

thanks for all the help guys. I got some 023 orings in and tried again but its still leaking out of the ambient pressure holes. i think i might just throw in the towel at this point. don't want to keep ordering orings i won't use for any other regs.

 

[redacted]

thanks for all the help guys. I got some 023 orings in and tried again but its still leaking out of the ambient pressure holes. i think i might just throw in the towel at this point. don't want to keep ordering orings i won't use for any other regs.

Take a good look at the sealing surfaces in the body and in the cap. You might be able to see a problem or feel rough spots in the cap with your finger. A Q-tip may also detect a rough spot. You may need to do a bit more cleaning. I have had some luck using brasso to smooth out a rough spot and restore function.

 

[ams511]

thanks for all the help guys. I got some 023 orings in and tried again but its still leaking out of the ambient pressure holes. i think i might just throw in the towel at this point. don't want to keep ordering orings i won't use for any other regs.

What is the duro on the o-rings you are using?

 

[runsongas]

90 duro viton from sterling seal and supply

 

[redacted]

90 duro viton from sterling seal and supply

The spec for that o-ring is 70 duro. Too hard an o-ring may not seal as well as a softer o-ring and will be more affected by small defects in the hard surface.

I only use 90 duro o-rings for a few HP seals. I avoid using them on LP seals. The only place I have found that often demands that hard o-ring is the piston stem o-ring on a balanced piston. I usually use 90 duro on tank valves since they are crush applications vulnerable to extrusion but have gotten away with 70 duro on the valve face.

 

[halocline]

I still think you need to check the IP for creep and try to figure out which of the 2 piston o-rings is causing the leak. If you have really bad IP creep that's going to put a lot of pressure on those piston o-rings.

 

[runsongas]

The IP isn't too bad, runs 140 psi. I tried scrubbing both sealing surfaces with metal polish but no dice. I'll give one last shot to the 70 duro orings.