Help! Another Scubapro MK25 whistling

[NozBzh]

Halocline, yes it only whistles when I inhale. I know it's not dangerous but as you say very annoying. I don't dive with it (it would look pretty bad in front of my Open Water students haha).

Before I got the new red stripe o-ring in place a couple weeks ago it was a continuous whistle with air coming out of the ambient chamber. The o-ring was worn out when I opened to reg to replace it. Now the whistling is not continuous and no leak from the ambient chamber, but still not the way it should be!

Andrewy, thanks for the tip but I already made sure of that.

 

[rsingler]

Harmonic vibration in the Mk25 Chamber originates with pieces of the regulator that can move in turbulent air flow. There are only two pieces that fit this requirement: the keeper spring between the seat and the upper spacer next to the HP Oring, and the upper spacer, (and I guess the Oring itself).
Harmonics may also arise in tightly coupled adjacent parts, e.g. the main spring. Finally, air flow itself can produce a whistle as it passes by the seat (think blowing across a Coke bottle as air dives down the piston bore.
Unless you are very sure of duro and quality, I would not substitute orings for the Red stripe one. The post where you noted air whistling from the ambient chamber meant a HP Oring leak, and that is very scary.
Among Scubapro's official known solutions, try these:
1) rotate the HP seat 180 degrees
2) confirm that the heavy main spring is "one side heavy". When you roll it gently on a flat surface, it should have one clear place where it rolls to a stop due to weight distribution. It may rock back and forth a little at the end. If it's perfecting symmetrical on the roll, change out the main spring
3) to minimize harmonic vibration of the keeper spring, bend it by holding each end and folding a little, so that it wobbles a little as you roll it across a flat surface. The idea is to brace one of the coils against the side of the reg body so that it is less likely to vibrate . Don't bend so much that it rubs against the piston shaft.
4) the last ditch trick that works with refractory cases is to cut the bottom spacer. Not the bushing that contacts the keeper spring, but the one that contacts the HP Oring from deep within the reg body (#23, PN 010.60.607). Take a razor blade or thin knife and slice from top to bottom anywhere along the circumference. Don't take a chunk out, or cut it in half just slice it once along its circumference. Once again, this changes the vibratory characteristics of the adjacent parts. This won't endanger the HP oring, and is an accepted technique in the toughest cases that Scubapro sees. As noted in a post above, make sure it is inserted so the for inner"bumps" are deep in the reg body and the beveled inner chamfer is against the oring.

 

[NozBzh]

rsingler, sorry for the late reply, I just saw your post.

Thanks a lot for all these suggestions. At the moment I don't have the tools to open my reg so it'll have to wait a week or two until I can try your solutions.

Very happy to have more things to try though

I'm in the process of moving back to Komodo from Sipadan so I won't be diving for a couple weeks.

 

[NozBzh]

Just a quick update. Elan who posted earlier on this thread sent me a duro 90 HP oring, but I haven't tried it yet (it arrived at friend's house). I just came back to Komodo and tried doing as rslinger suggested. I first rotated the HP seat, but when I turned the air on it was leaking like crazy so I quickly turned the air off and put it back in its original position. When I tested it again, it was leaking from the top (where you adjust the IP) and still whistling. I then tightened the screw that adjusts the IP, it was still leaking but the whistling was gone. I opened the top part again, took out the IP screw completely and put it back together. This time no leaking or whistling!

I'm not quite sure how that is possible since prior to this I completely took the reg apart and cleaned everything 5 times and nothing made it stop whistling. I'll wait to see if it stays like this because I remember when I started to have the whistling problem if I loosened up the top of the reg to the point where there was a slight leak, the whistling would stop. As soon as I tightened it again the whistling would resume.

I'll keep you updated.

Thanks to all who contributed to this thread and helped me fixing my reg.

 

[rsingler]

NozBzh,
I have to tell you, and I don't mean to offend, but you're scaring me a little here. I'm not sure you want to dive that reg at all.

I first rotated the HP seat, but when I turned the air on it was leaking like crazy so I quickly turned the air off and put it back in its original position.

Rotating the seat should involve almost no change in any sealing component. The HP sealing oring around the seat should slide easily during this maneuver. "Leaking like crazy" (from where not specified) makes me think that you have a high pressure leak around this oring, since that is the only component that should have moved during this adjustment. But whether it is the oring or a scratch in the body where the seat seals is not clear. See this next:

When I tested it again, it was leaking from the top (where you adjust the IP) and still whistling. I then tightened the screw that adjusts the IP, it was still leaking but the whistling was gone. I opened the top part again, took out the IP screw completely and put it back together. This time no leaking or whistling!

With adjustment of the cap and IP screw, you are theoretically changing where the HP seat sits in the body. You didn't specify whether you set your IP back to where it was before this started.

I remember when I started to have the whistling problem if I loosened up the top of the reg to the point where there was a slight leak, the whistling would stop. As soon as I tightened it again the whistling would resume.

This kind of maneuver is very dangerous. It means you are letting the HP seat rise in the body to a position where air is leaking around the oring. I don't know how you obtained a reasonable IP with this, but I would never let the HP seat cap sit loose in the body.

Thinking off the top of my head, there are only three dynamic spots in this regulator where it can leak (I may have missed another):
1) HP seat oring (or adjacent body scratch): high pressure leak from IP adjustment cap - dangerous
2) HP piston shaft oring (red stripe oring): high pressure leak from ambient holes - not good if something is chewing up the oring. Potentially catastrophic.
3) Piston head leak at oring or scratch inside the piston cap - again air from ambient holes. Probably not catastrophic, but wastes air and frightens people.

The whistling sounds to me like a issue with your HP seat position or shape, or the underlying spring. I say this based upon your previous maneuver of loosening the seat cap, because if you are setting the IP back to its original pressure, then the HP seat should be pushed to its original position by the hex screw, no matter whether the cap is tight or loose. And that leads me back to a possible scratch inside the body where the HP seat and oring seal.

I'd really recommend that you have a Scubapro guy familiar with this reg take it apart for a close inspection. A parts change without a logical sequence as you track down your two issues is just asking for trouble.

Again, sorry if I offend with my comments, but I'm concerned for your safety if you dive this reg.

 

[NozBzh]

rslinger, just to be clear, I haven't dived that reg for a while.

I did maybe 3 dives just after it was serviced by a Scubapro tech (and PADI Course Director) and it whistled, then I didn't dive for a few weeks. Before diving again, I tested it on land and it didn't whistle anymore. I dived with it for a week and then it whistled again. Since that time I have't dived with it. I just take a reg from the dive center.

Now about that HP seat rotation, you say it should involve no change in any sealing components. When I turned it, it didn't look right to me. The seat has a little groove on the top that fits a bump on the metal spacer that goes on top of it (PN 10752102). After rotating it 180 degrees the spacer doesn't really fit, which to me is the cause of the leak. After I put it back together, I turned off the air very slowly and as soon as I heard the big leak I turned it off. I didn't specify where the leak was from since I didn't spend time trying to locate it, I could be wrong but I was sure it was because the metal spacer doesn't fit the other side of the HP seat. I would also say it way was a HP leak, I assume the spacer pushed the seat sideways, which allowed the air to leak on the side of the seat (between the body and oring). I may not have understood what you meant by rotating the HP seat, so if I did it wrong I'd be happy to hear what you meant.

I the IP screw was set back to where it was after the reg was serviced (when the whistling started). I checked my IP, it is 9,5 bar.

Again, all this was done in a workshop, and I haven't dived with this reg. I know loosening the cap creates a leak because the HP seat rises too high. I was just trying to understand why my reg was whistling when everything should have been fine. I didn't try to obtain a reasonable IP at all, I was just trying things to see what would make the whistling stop and why. I wouldn't dive with a HP leak on my reg!

My reg was serviced twice by two different Scubapro techs. The first time it worked for 2 weeks and then leaked from the ambient chamber. I took it back and he fixed it, but charged me for it. I then wanted to learn how to do it myself so I did my equipment speciality instructor course with a scubapro certified course director who taught me how service a MK25 while he worked on mine. That's when the whistling started.

No offence taken, I know messing with regs can be very dangerous. It's just that my experience with scubapro techs wasn't great. And where I am now, the only way to find a tech is to take a 2 hours flight so it's not like a 20 mins drive to a local dive store.

I did a complete rebuild with new parts several times to see if it would fix the issue but it didn't. I was not changing random parts. The only random change I did was rotating the HP seat (but as I said before I might have done it wrong, in which case it would be helpful if you can clarify).

Thanks

 

[halocline]

My schematic does not show that part number, but I have an old schematic. I'm also having a hard time understanding what you're describing. Are you saying that there is a constant whistle or only a whistle (more like a harmonica) when you breathe?

A leak at the seat retainer is likely to be pretty aggressive sounding, almost like a blown tank valve o-ring. And when you say 'rotate the seat" are you talking about turning it over so that the piston contacts the other side, or turning it clockwise/counterclockwise like a knob while it's in the seat retainer. If you're flipping it over, there's one problem. What do you mean by "cap", are you referring to the seat retainer?

Once you put it together, if it's whistling, can you submerge it in a tub of water and determine where the bubbles are coming from?

These things are just not that complicated; HP air can only leak out of the o-ring installed on the seat, the HP o-ring on the piston, the yoke/DIN retainer o-ring, a HP port plug, or out the seat itself into the IP chamber, in which case you'd have IP creep, probably a lot of it.

 

[NozBzh]

Halocline, my schematic is from January 2011, I got my reg in March 2011 so I assume that's the one I should use.

As for my problem (which seems to be fixed now), it was whistling upon inhalation (or pressing the inflator button). However, there was one instance where it whistled continuously (the HP oring was worn out). After using a new red-striped oring, it was back to whistling only during inhalation.

The leak I heard after rotating the HP seat was indeed pretty aggressive. But I suspected it might leak so I opened the air very slowly and closed it as soon as I heard it (and I didn't try to locate the leak).

I'm also confused by what rslinger meant by "rotating the HP seat 180 degrees", but my understanding was flipping it over. Let's wait until he comes here to clarify this point.

Yes sorry by "cap" I meant seat retainer.

I did submerge it yesterday but the whistling was gone and no bubbles were coming out. At the time it whistled during inhalation I didn't submerge it but I seem to remember it didn't leak, just whistled (which would be coherent with some said here, the sound is created by vibrations inside the reg body).

 

[halocline]

You can't flip that seat over. One side is machined (or molded) to precisely fit the piston edge, the other side is not. Trying to pressurize the reg with the seat upside down wouldn't be much different than just connecting a 2nd stage directly to the tank....not so good.

I don't work on these too often, I don't own one, but the seat I'm looking at now has a small dimple on the side that fits in the seat retainer. But you shouldn't confuse this with any sort of recess to fit the piston; the two sides don't look at all similar, it't not like a flat puck seat that you can flip over to use the other side.

Rsingler was suggesting that rotating the seat, meaning turning it like a volume control knob while it's in the seat retainer, might subtly change the resonance between the piston and seat, quieting the whistle. Again, it's not really a 'whistle' its more like a harmonica. I don't know how much you understand about the causes of the harmonica sound (bet you're learning a lot!) but it's because air moves very fast over the piston edge when it opens up, and this creates vibrations. This is similar to how woodwind instruments like flutes work, and when conditions are right, there's enough vibration and resonance to cause the 'musical' sound. It's not a leak at all. If you have any sort of leak, your problem is different. A leak and the harmonica sound? That means two different (but maybe related) problems.

All the tricks like re-lubing the o-ring, moving the seat, bending the small spring (that's a good one, rsingler, BTW, and so is the check to make sure the main spring is not 'balanced') etc...are to disrupt the resonance that occurs with this quick air movement through the piston. It's not just a MK25 problem, all piston regs are susceptible to it. My MK2 sang like a nightingale after a rebuild once.

Anyhow, best of luck and hopefully the problem is solved.

 

[redacted]

I then wanted to learn how to do it myself so I did my equipment speciality instructor course with a scubapro certified course director who taught me how service a MK25 while he worked on mine. That's when the whistling started.

I did a complete rebuild with new parts several times to see if it would fix the issue but it didn't. I was not changing random parts. The only random change I did was rotating the HP seat (but as I said before I might have done it wrong, in which case it would be helpful if you can clarify).

As for my problem (which seems to be fixed now)....

The leak I heard after rotating the HP seat was indeed pretty aggressive. But I suspected it might leak so I opened the air very slowly and closed it as soon as I heard it (and I didn't try to locate the leak).

I'm also confused by what rslinger meant by "rotating the HP seat 180 degrees", but my understanding was flipping it over. Let's wait until he comes here to clarify this point.

What could you possibly have learned about how your Mk25 works, troubleshooting, and repair that made you think you should rebuild it with new parts "several times" and flip the seat over??? That is alarming.