I just can’t seem to help myself from finding cheap MK7’s on eBay. My latest one was just $15 plus shipping. The seller, who I’ve bought from before, accurately described it as “for parts only.” In the past, though, I’ve been able to bring his offerings back to life.
This one was a challenge. It was covered in vertigris and had an ip of 150psi. I took it apart and was pleased that the inner chambers were relatively absent of corrosion. The o-rings were in pretty bad shape with a couple of them breaking as I was removing them. The real hard part, however, was with the hp piston shaft o-ring.
I started with a typical brass pick, trying to get behind it to pull it out. After about an hour unsuccessfully working on it, I realized this was going to be a problem. The o-ring was more like plastic than rubber and fused on all sides of the land. A brass pick just wasn’t going to do the job. So,I grabbed my steel double hook pick, knowing it would make short work of the nasty ring. Nope, trying to get the pick around it wasn’t working and I almost bent the pick before giving up. I was convinced that this is the original o-ring and at least 45 years old. I now realized I would have to do the unimaginable. I pulled out my wife’s stainless steel dental pick and carefully proceeded to break up the o-ring piece by piece. I realized that I’d probably destroy the land, but nevertheless felt I had no other options.
Finally, after another hour I got it all out. Because the land is deep in regulator, I wasn’t sure if if I had scratched it and rendered the regulator useless. I cleaned all the parts and put everything back together. I added two shims. When tested, the regulator psi was still at 150, but holding. Arrh, I have to disassemble it to remove the shims. Putting it back together, even with a piston bullet, I cut the new hp o-ring. Now I have to start over and go into the hp land, something I really didn’t want to do. I put in a 90 duro from VDH this time and it goes in easily, (thanks Bryan). I put the regulator back together.
Testing this time gives me a solid 138. I’m encouraged that maybe I didn’t destroy this regulator and might actually get to use it. Sits overnight and still at 138. But, I had to do a wet test to see if leak bubbles were going into the ambient chamber. One hour in the bathtub and no bubbles! Success and this MK7 is back from the dead, ready to dive again.
Thank you, rsingler for the outstanding tutorial. I’m out of my lane when it comes to Scubapro as I exclusively tinker in vintage US Divers regulators. But, after receiving inspiration from experts such as couv and Herman, I purchased a cheap “for parts Only” MK5 and MK7 on eBay. Happily, both were rebuildable.
