Nemrod Snark III leaking air

[menemsha1968]

Does anyone out there have experience with the Nemrod Snark III? I purchased one, brand new, at a dive store in the late nineties. Or maybe it was early 2000s. Can't remember for sure. I just remember that it was the last one they had, and it was the latest and last version. All of the hoses, check valves and the diaphragm are made of silicone, and the cans are constructed of a thicker gauge than my US Divers regs. It is very well constructed, and I was very impressed by it's quality. Anyway, I added a SPG and a BC inflator hose to it, and I dove with it only a few of times a year, for a few years. I always kept it clean and dry when not in use, and put a light film of silicone grease on all of the check valves and diaphragm, for good measure. It's been cared for, and not used much. The last time I did tinker with it, I removed the over pressure relief bleeder valve to clean and inspect it. Immediately upon re-installing the OPR valve and attaching a full tank, the second stage demand valve started leaking air. Seemed like a weird coincidence that the second stage seat would all of a sudden go bad, right after tinkering with the reg. I've since taken apart the whole regulator, cleaned, inspected, and reassembled it a dozen times, and cannot find anything wrong with it. The LP seat for the second stage looks fine, and so does the mating surface of the orifice it makes contact with. It is of an unbalanced, upstream poppet configuration. The orifice is a flat, brass surface with a round hole, and the poppet is a perfectly flat, hard rubber (or maybe silicone?) disc that is larger in diameter than the orifice which it blocks off. No weird shape; very simple design. The poppet stays shut by spring pressure, and presumably, the intermediate air pressure. But no matter how well or often I disassemble and clean everything, it still bleeds air. I even installed a heavier spring, to no avail. Any suggestions? Thanks.

[Herman]

Welcome to VDH.
I don't have much experience with Nemrods but as fate would have it, I happened on my long forgotten Nemrod service manual yesterday and have it at hand. Looking over the parts and drawing (and reading the service section of the manual)there are only 2 real ways the second stage can leak, either a bad seat/orifice interface or a mis-adjusted second stage levers. The manual also suggest an overly stiff diaphragm may cause the problem. First thing to do is open the cans and test the reg, if it leaks with the diaphragn off, you have a seat issue, if not then lever height is the next suspect. The manual indicates you set the levers using a special gauge....I am making a SWAG but I suspect setting them so there is a small space (1/16-1/8)between the lever and diaphragm would do nicely. With the reg under pressure,set the diaphragm on the reg and gently press down/tap the diaphragm to feel/hear how much space you have between the lever and diaphragm. Not scientific I know but it works nicely on USD regs (with a little practice).

[menemsha1968]

Hello Herman, and thank you. I also found, and downloaded, the Nemrod material (that you reference) the other day, and found it helpful. And yes, it leaks air with the cans separated (the demand levers just fall out of he way) and nothing contacting the push pin that operates the seat. With that pin exposed, I can push on it directly with my finger and listen to the volume (and feel with my hand) of the air hiss fluctuate. The air leak is definitely coming from the orifice/seat interface. The only thing that I suppose I can do now would be to try a new poppet (or re-manufacture this one, which, BTW, does not have any visible indicators that it has taken on a deep "set" through wear that could be leaking) and/or resurface the hard orifice. None of which I have, or know where to find, the machinery to do. Any suggestions where I should look? Thanks.

[Herman]

My guess is the soft seat has gotten hard and is not sealing well. Your option is to replace or repair it. We use to have a memeber on the board that lives in Spain and had access to parts, he may show up and give you a hand.
I would HIGHLY recommend you avoid touching the hard seat unless you are absolutely sure it has a problem. It is unlikely that it does and the odds are good you will make the problem worse and once you change it, there is no repairing it. Study it closely with a high power magnifying glass for any nicks but unless saltwater has gotten into the second stage that caused corrosion, the odds of it being the problem are slim.

I know you want to keep the old girl going but in the end, finding a good DA or RAM and restoring it is your best option to keep diving a DH reg. Pretty much any part you need for those are readily available or if you would like the latest and greatest DH, the Argonaut Kraken will be available again soon.

[sitkadiver]

Just out of curiosity, do you have a means of checking the IP? I know you stated you had reassembled the reg a few times.

[Herman]

Since the Nemrod uses an upstream second stage valve, high IP would tend to close it tighter, not cause a FF as most regs do. And the OPV on it is not leaking so an excessive IP is not likely.

[sitkadiver]

Thanks Herman. I was under the impression that there was a spring on the lever side and since the RO said he had it on a full tank, I assumed the IP would be inversely lower...

Anyway, I just looked at the diagram in the files section and do not see how the OPV and leak could be related.

I guess the good news is that Rob has the the seat/poppet's in stock.

Good Luck and please let me know how you get fixed, I enjoy these learning exercises.

[Herman]

I didn't know Rob had them. menemsha1968 (sorry don't know your name), Rob (aka realivan1969) has them listed on his web site. Shoot him a PM and ask about them. here is a link, scroll down a ways to see the seats. http://www.thescubamuseum.com/products/products.htm

[swimjim]

The IP can be checked by removing the over pressure valve, screwing in a BC hose and running an IP gauge off of that. Proper IP if I remember correctly is about 142 psi. As the reg is unused and has been sitting for a long period, it is very likely that the lp seat has hardened with age.
I have a Snark III Silver and it's an excellent reg. Certainly a good diving reg. If this one were mine and the leak is just a trickle, I'd dive it in a pool. I think it's possible that by cycling the regulator, the seats may take a "set" once again.

[menemsha1968]

Hey guys, thanks for all the input. I picked up a 320 grit rod shaped stone from a machine tool supplier, and was going to try to resurface to orifice, but if there is someone that I can get a new seat from, I'm definitely going to try that first. And yes, I do have an IP gauge attached; it's within range. Although the OPR valve and the second stage are unrelated, it just seems too coincidental for the timing of the leak. I cannot help but wonder if, when I removed and reinstalled the OPR valve, a miniscule bit of the new chrome flaked off and found it's way into the orifice/seat interface, and is now embedded into one or the other, or maybe caused a tiny nick in the orifice. As I stated earlier, I'm not able to visibly detect anything that is obviously awry with either part, but that doesn't necessarily mean it's not there. I'm going to try replacing the rubber seat first, and if that doesn't solve the problem, then I don't see where I have much other choice then to attempt to resurface the orifice. Any other ideas or thoughts would be welcome.

[antique diver]

I would try a new rubber seat before taking the abrasive to the orifice. Might also want to try a rubber pencil eraser on the orifice to see if that helps. The 320 would be the last I would try because it could cause damage to a perfectly good orifice if something else is the cause of leak.

[Herman]

I don't mean to be redundant but unless you are absolutely sure the orifice has issues don't touch it, the chance of damaging it is too high. If you can't see the problem with a lot of magnification DON'T "fix" it. When I have to polish orifces I use 1500 to 2000 grit wet dry sandpaper on a jig I made to do just that. The seat must be kept square with the seat holder which is not easy to do by hand. Lower grits tend to leave microscopic scratches that are IMO to big leaving leak paths and the lower the grit the more chance of you being accidently overly aggressive. The seat depends on a sharper edge to seal, the more it gets rolled off, which you willl do if you polish it, the more difficult it is to get to seal, esp with older, less soft seats. It is pretty rare for a hard seat to have an issue unless it has been subject to saltwater corrosion or someone has carelessly dinged it up.

[menemsha1968]

Thanks guys. Just got a hold of Rob, and sent him the money for a new seat. I also used a brand new pencil eraser to clean my orifice. (wait a minute - that sounded a bit unseemly) Rather, I used a pencil eraser to clean the orifice in my regulator, and it reduced the leak rate a little bit. Hopefully when the new seat gets here, it will solve the problem. I really don't want to have to use a hard abrasive on this thing.

[antique diver]

Thanks guys. Just got a hold of Rob, and sent him the money for a new seat. I also used a brand new pencil eraser to clean my orifice. (wait a minute - that sounded a bit unseemly) Rather, I used a pencil eraser to clean the orifice in my regulator, and it reduced the leak rate a little bit. Hopefully when the new seat gets here, it will solve the problem. I really don't want to have to use a hard abrasive on this thing.

Hmm, I would recommend having one eraser reserved just for your regulators.

[menemsha1968]

Yeah, that's probably a good idea. I'll keep track of it.