ams511
Contributor
Probably the biggest challenge in rebuilding the MK5 is removing the old HP piston o-ring cleanly without scratching the journal it sits in. I wonder how many MK5s were ruined by careless techs digging out that o-ring while answering the phone. I use the scubatools double hook o-ring pick for that; it works great. I just bury the point of the pick in the old o-ring so it never comes near the metal and ease it out.
I bent a pin that came with a shirt and stuck the oring slightly. It worked like a charm and was not a challenge to remove the o-ring at all. To install a new one I used the piston bullet to push it into place, it worked well too. I was surprised how easy it went.