Advice on old MK2/R380

[topher10]

I took a chance and spent $50 on a craigslist MK2/R380 setup, which also includes a scubapro octo and gauges that I probably will not use. Pictures below. My goal is to use it as a pony reg and perhaps as a backup to carry around in case my primary regulators fail while on vacation. I also thought it would be a good intro for servicing my own regs without much risk since the worst case is I am out $50.

Good news: Everything works. Cleaned it, put it on a tank, regs hold pressure, can breath off and feels normal. The R380 second stage in particular seems fine and fairly clean. Hoses will need to be replaced but I expected that. I admittedly have not opened anything up yet and I also do not yet own an IP gauge. So there could be underlying problems

Bad news: MK2 first stage has a lot of surface corrosion, and there is a steady stream champagne bubbles leaking from where the tank meets the reg (Yolk Nut). There is a lot of corrosion there and I am worried that there is enough pitting that it will never seal. No leak from the opposite side (ambient chamber). Thankfully there is no obvious green on the inside (mesh) of the reg, but admittedly its hard to see.

Questions:
1. Is it possible to replace the yoke nut/retainer nut that is so corroded? I found a part number (P/N 10103115) from a different thread, but not sure how to buy it. Google search brings up sites I am not familiar with.
2. I am worried about the piston or other internals. Is there a point of no return for the spring or piston, and if so can one buy those parts individually?
3. If I buy the service kit, clean and replace everything, put it back together and have a stable IP in the correct range and no leaks, then is there any reason not to use it?
4. Is an MK2 of this vintage and condition worth the trouble? Craigslist can be a dangerous place.

Thanks for the advice.

 

[shurite7]

1. Yes, the yoke retaining nut can be replaced.
2. Springs do wear out over time. Yes, the piston and spring can be replaced as needed. Any individual component of the reg can be replaced.
3. From the looks of the reg it needs to be taken apart, cleaned thoroughly, which will remove the corrosion build up, o-rings and hp seat replaced, and then adjusted. So long as there is nothing drastically wrong with the reg you should be able to use it for many more years.
4. This isn't a vintage Mk2. Maybe older, but there are plenty of these being used around the world.

The Mk2 is a workhorse and can take a beating which makes it a good rental or pony reg. Anytime one buys a used reg online he/she should have it serviced. Good luck and have fun.

 

[tbone1004]

1. yes, @OWIC647 can probably help you with that
2. yes, but it'd probably be leaking, again @OWIC647 can help you out
3. no
4. a mk2 is a mk2 is a mk2 basically. No reason to not use it as long as it behaves itself

 

[herman]

A bit of a clarification, while the yoke nut is a little messed up there is NO reason to replace it. It simply holds the yoke on. Any leaking from that area is from 1 of 2 reasons, a bad tank oring or a damaged face on the main body of the reg. Based on your last photo, the main body to tank interface appears to be damaged. This is not a big deal. Once you have the yoke nut and yoke off, you simply polish the surface flat using 400 or greater sand paper held down on a flat surface. You will likely remove most, if not all the chrome but that is really not a big deal, looks bad but has no impact on the operation of the reg. Based on the rest of the photos, the reg does need a good cleaning and a parts kit but odds are, once that is done, it will be a perfectly functioning reg. MK2s are hard to kill. Unless the hoses are cracked or leaking, I wouldn't replace them.

 

[WantSomeScuba?]

4. a mk2 is a mk2 is a mk2 basically. No reason to not use it as long as it behaves itself

Doubles as a blunt force instrument in a pinch as well. There's some older regs I shy away from when they start getting to that stage, but not that one specifically.

Keep a torque wrench handy, though.

 

[rjack321]

Unless the hoses are cracked or leaking, I wouldn't replace them.

Who knows the age of those hoses. Like any soft part they get old and tired, the last thing you want in a pony bottle system is for it to not be solid when you need it. Hence I would replace the hoses to avoid ending up in DAN's "we know maintenance is good but skip it to be cheap column"

Inflator failures, burst hoses, the breakdown of hose liners and many other equipment issues that timely maintenance would have caught all documented here:
Scuba Diving Incident Reports and Prevention | DAN

 

[herman]

Who knows the age of those hoses. Like any soft part they get old and tired, the last thing you want in a pony bottle system is for it to not be solid when you need it. Hence I would replace the hoses to avoid ending up in DAN's "we know maintenance is good but skip it to be cheap column"

Inflator failures, burst hoses, the breakdown of hose liners and many other equipment issues that timely maintenance would have caught all documented here:
Scuba Diving Incident Reports and Prevention | DAN

The age of the hoses is not a big deal, to start with, based on the age of the second stages, they are not that old. Many of us are using hoses 20 or more years old that are completely serviceable. This has been discussed on SB before and it was pointed out, that new hoses have in fact failed too. While sudden catastrophic failure is possible, the majority of failures start as a slow and progressing leak. As long a the hose looks in good shape, is not hard or leaking, there is no good reason to replace it "just because I don't know how old it is". The ones that were failing in a few years were the newer Miflex type hoses, not the older style as these are. How many of us are driving cars that are 10,15 or even 20 years old that use basically the exact same hoses on our brake lines, I have never heard anyone recommending they be replaced every few years, if lots of accidents were being caused by failed brake hoses, we would surely be hearing about it. Brake lines are much less easy to inspect, operate under a lot worse conditions and IMO, a failure of them is much worse. Don't get me wrong, I am all for good maintenance but swapping parts that do not actually wear out but rather are replaced "just because" is rarely a worthwhile venture for anyone other than those who sell parts.

 

[topher10]

Thanks to all for the responses. Its nice that the first 4 responses say that the reg has a good chance of being usable.

My plan now is to see if I can get it open without breaking anything, and then look at and clean the internals. If things seem OK, I will get a service kit and an IP gauge, put it back together, see how it looks, and if OK try it in the pool. If I hit a snag along the way I will post back and seek advice (DIY Forum?), but I am more than willing to send it to a professional for this first overhaul.

RE: Hoses. The hoses do have small cracks throughout, consistent with drying out. I am not sure they are at risk of catastrophic failure, so we will see. I might simply need different lengths to match my intended use, just haven't gotten that far.

Thanks again.

 

[rhwestfall]

You could also convert it to DIN (about $35, IIRC for the SP Universal DIN which fits it)..... It takes a significant bit of effort to kill a MK-2. Silly simple and robust as all heck. Have fun. One thing to understand is that the MK-2 uses shims to adjust IP, so if it isn't in spec (low), you need to have access to them. The rebuild kit is at VDH, and there may be a schematic and rebuild info there too (if not then Frogkick gas them).

I just rebuilt two MK-2 stages that were going on 4 years of abuse. Took me about 25 minutes each to tear down, clean, and rebuild, most of the time being in the ultrasonic and scrubbing/rinsing.

 

[АлександрД]

first - use Citric Acid and hot water.
Put all disassembled parts for 5-30 min in to hot strong liquor of Citric Acid. Stay there for 5-30 min, time to time shaking and mixing parts.
Important notice: Do not mix together steel and brass parts. In case of contact them together - it makes galvanic couple, and you can lose all chromium layer from details.
Next clean for 1 hour in to clean fresh water.

second - use polishing tool, e.g. Dremel or cheap one, like described here Air Barrel question - corrosion? Scubapro G250V

Next assemble it back and getting pleasure.