US Divers Regulator Self-Service

My regs were starting to leak when the tank was full. I decided to take them apart and service them myself, because (1) it costs $250 and takes 2 weeks here and (2) I wanted to do it myself. I have a US Divers setup from ~1995. They say "Calypso" and "Aqualung" on the second stages and are super easy to tear down and rebuild.

DISCLAIMER: I hate disclaimers.  Don't follow these instructions, whatever you do!!

UPDATE: Leaking regs is a sign that the 1st stage is beginning to fail, which increases the pressure behind the 2nd stages, leading to leakage.  Have a local professional service the first stage.  After seeing how many bits they replaced, I can confidently say that I wouldn't want to do that part myself.  It cost $100 (parts + labour) to do in Australia, would probably be much less in the US.  Now my setup is flawless and breathes so easy.

1. First, unplug the hold plugger (not shown) opposite the valve by pinching the two tabs inside the reg together and pushing out from the inside while prying with your fingernail on the outside.
2. With this out of the way, you can reach through the hole (just opened) with a 1/4" drive 1/4" socket on a screw-driver handle and take the self-locking nut off the threaded shaft. Make a note of how many threads were exposed before removing it, so you know how far to twist it back on.
   
   
3. Remove the now-loose lever arm and washer. Note that the washer comes off first, then the lever arm.
4. Use an adjustable wrench and thin rag (to avoid scratching chrome) to loosen the larger of the two hex areas on the outside of the reg, where the hose connects to the reg. You will have to grip the reg's plastic body firmly, to react the torque you are applying. This will detach the hose from the regulator, making subsequent steps easier. In fact, you might do this step before step (1).
   
   An exploded view of the dissasembly up to this point is shown below. Note that the most important part (vale assembly) not yet removed from the regulator housing.
   
   
5. Again with the adjustable wrench on the outside of the housing, loosen the remaining hex area by firmly gripping the housing and using a rag to avoid scratching the chrome.
6. Remove the part you've just loosened, which releases the valve seat. spring. plunger gasket and spring seat parts.
   
   
7. Clean the entire area where the plunger and valve seat interface with vinegar and a kebab stick (or toothpick would be better). Don't use any metal tools in this part, only wood or fingernails and Q-tips. The vinegar gently dissolves the calcium which will have built up, preventing sliding motion of the valve due to "Stiction" (static friction).
8. Lubricate the sliding interface with lip balm. Don't use any petrochem stuff, because you are going to be breathing this stuff in for a bit. Petroleum can worsen "rapture of the deep." Jacques Cousteau has a fantastic story about this from some of the first cave diving experiences, where their compressor ingested exhaust and it fucked them up, big time. Not same, not different. Use hippie stuff, like Burt's Bees hand salve.
   
   Once you've cleaned both parts, insert the plunger and gently spin it around at some angles (it's a spherical joint) to make sure it doesn't hang or catch at all. It should make a jingle sound when you do this.
9. Put the internal component of the valve assembly back into the housing. Note that you can choose what side to put it in. Should be the same side for both regs.
10. Put the spring into it from the outside.
11. Put the plunger through the spring, and through the internal valve guide. It is important to align the flat sides of the valve stem with the flats in the valve stem guide before tightening things up, to avoid pushing the valve stem guide out or damaging it.
12. Lube the threads of the valve seat part lightly, and thread it into the valve guide from the outside of the housing, compressing the spring and seating the plunger.
13. The rest of re-assembly is basic, you can do it. Lube and clean everything lightly beforehand. Tighten the 1/4" self-locking nut slowly, feeling the lever arm for free play. Just when there is no free play, stop, and make sure the same number of threads are exposed as before assembly. This action will be tested in the next step.
14. Put the regs on a full tank and do the "Cracking Pressure" test. Turn the mouthpiece towards the sky, and slowly lower the back of the reg into the water. It should start free-flowing once the back is submerged about 1/2" ~ 1".