MK5 Service Issues

[Michael Ward]

I have a late '70's MK5 that I recently sent in for routine service, and it ended up being returned to me marked as "unserviceable", due to a bad piston. I thought that to be a very vague explanation so I called the service center for a better answer and what I got was that they were unable to get the intermediate pressure to stabilize, due to the piston being bad, whether from a worn knife edge, or any other slight deformity. Apparently Scubapro has discontinued support for the MK5 first stage and the replacement piston is not available. I thought I was SOL until I came across a MK5 piston for sale on ebay that was rescued from an old dive shop. I called the service center back to let them know I had a replacement piston and I was told they still cannot service it since the part didn't come from Scubapro and they don't know it's history, valid point I thought.
Anyway, I've since thought maybe I'd have better luck taking it to a different shop. Is this a waste of time, and should I just cave and replace my 35+ year old reg? Has anyone else experienced similar issues?

 

[cerich]

It can most likely be serviced, the shop just doesn't want to. AWAP here is the guy to talk to

I have a late '70's MK5 that I recently sent in for routine service, and it ended up being returned to me marked as "unserviceable", due to a bad piston. I thought that to be a very vague explanation so I called the service center for a better answer and what I got was that they were unable to get the intermediate pressure to stabilize, due to the piston being bad, whether from a worn knife edge, or any other slight deformity. Apparently Scubapro has discontinued support for the MK5 first stage and the replacement piston is not available. I thought I was SOL until I came across a MK5 piston for sale on ebay that was rescued from an old dive shop. I called the service center back to let them know I had a replacement piston and I was told they still cannot service it since the part didn't come from Scubapro and they don't know it's history, valid point I thought.
Anyway, I've since thought maybe I'd have better luck taking it to a different shop. Is this a waste of time, and should I just cave and replace my 35+ year old reg? Has anyone else experienced similar issues?

 

[redacted]

One thing that troubles me is how a regulator can be sent in for "routine service", which I assume means it was working OK when it went in; and it come back with an unserviceable piston. I suspect I know how that happens which is one reason I got into DIY.

I would also be a bit skeptical as to how they know the problem is the piston rather than the seat. In either case, a new piston and maybe a new seat could give it another 35 years of service. I really don't understand the shop's excuse for not fixing it for you. I would have to wonder if they damaged your regulator and refused to repair it with the replacement piston you found just so they could sell you a new regulator.

One thing you might do is get a good magnifying glass and inspect the knife edge of the old piston. I does not take much damage to cause a bit of IP stability problem. If it was dropped, the damage should be fairly obvious and the piston will need to be replaced. But if it was something like a small nick like could happen during cleaning, then it is possible the knife edge could be cleaned up and that old piston restored for use. In any case, time to find a better source for service.

 

[halocline]

Anyway, I've since thought maybe I'd have better luck taking it to a different shop. Is this a waste of time, and should I just cave and replace my 35+ year old reg? Has anyone else experienced similar issues?

If the IP wasn't creeping when you brought it in and it is now, that's definitely the shop's responsibility. Whether or not they will accept it, who knows, and can you prove the IP was stable when you brought it in?

The knife edge on those pistons is pretty delicate, and a tiny imperfection will cause IP creep, so it does happen from time to time that the piston needs to be replaced. But you can sometimes clean up the edge of the piston pretty easily, I've done it on several MK10 pistons. If you're handy and looking for a new hobby, you could spend far less money on a few tools and a book than you would on a new regulator, and have a go at it. There are several folks on this forum that can give you good advice.

If your MK5 is the later version with 5 LP ports and 2 7/16" HP ports, it's an especially desirable regulator and worth saving.

 

[Michael Ward]

Thanks for the detailed reply, I think I'm going to give it to another shop and see what they come up with, if it does need a new piston, Hopefully they use the one I have.

Normally I would be just as skeptical as far as the shop not repairing it, so they can sell me a new reg, but the place I send it to is a service center only, and does not sell equipment, a major plus I always thought. I've had my reg serviced there before and have always had good experience.

Also, yes It does have the 5 LP port turret and 2 7/16" HP Ports.
I can't confirm the IP wasn't creeping before I had it serviced, I last used it in October.

 

[elan]

If you posses basic mechanical skills its easy to rebuild this regulator with few basic tools. Luckly we have few people here who are very knowledgeable and helpful. Some of them have replied to this post.

 

[scubafanatic]

Bryan @ vintagedoublehose.com is in the business of servicing/repairing vintage regs, contact him.

 

[herman]

awap/halocline,

Do either of you know if the piston is stainless or chrome plated brass?
If you have a piston that is beyond repair on its edge, lets talk off line, I am wondering if it can be acceptably repaired. I have an idea on how it might be.

 

[Michael Ward]

I got an exhaust tee for my R109 from vintagedoublehose, and found some tech manuals and drawings too. Pretty cool shop. Good to know he does servicing as well.

 

[ams511]

awap/halocline,

Do either of you know if the piston is stainless or chrome plated brass?
If you have a piston that is beyond repair on its edge, lets talk off line, I am wondering if it can be acceptably repaired. I have an idea on how it might be.

Herman there was a technique named "Matt Magic" which brings old pistons back to life.