Scubapro MK 5 1st-stage leak, probable cause and repair ?

[scubafanatic]

Hello,

I've acquired a few of these 1st-stages and had them serviced this summer, now I'm finally getting a chance to do underwater bubble leak tests in the tub, and have so far found one 1st-stage leaking bubbles from the 1st-stage ambient chamber holes. (this leaking one has the 4-hole non=SPEC ambient chamber) It's a subtle leak, too small (so far) to be detected via SPG/AI computer or audibly, but it's definitely visible underwater, emitting a 1/8" diameter bubble every approx 10-15 seconds from one of the 4 holes. The bubbles are coming from the LP swivel turret side of the 1st-stage. I don't think the leak is related to the turret, I suspect it's coming from the HP piston O-ring.

I know it's a minor leak, but it still bothers me, especially as it could be the precursor to a much bigger leak with usage/passage of time.

Hopefully it's just needing another new piston O-ring, and not that the piston or chamber is scored in any way.

IP starts @ 125 PSI, gradually creeps up to 135 PSI and locks @ 135 PSI. Tank pressure approx 3000 psi.

Would you agree in my probable diagnosis ?

Thanks in advance!

Update: OK I timed the bubble interval @ 1 bubble every 30 - 35 seconds.

 

[John C. Ratliff]

It's probably the main piston O-ring, but you need to check the inside of the piston chamber for corrosion too. It probably has some buildup that needs to be removed. Others on the board are much more experienced than am I on this, but that is my best guess.

SeaRat