Help! Another Scubapro MK25 whistling

[NozBzh]

Hello

I have already searched this forum and found several threads about whistling MK25 first stages. I found them very helpful but unfortunately mine is still whistling.

Here is my problem: my mk25 is whistling when I inhale (or press the purge, or inflate my BCD). My Course Director (who is a Scubapro certified tech) serviced my reg and taught me how to do it in the process while teaching me the Equipment Specialist speciality instructor course.

It was fine during the tests on land, but during my first dive I noticed it whistled when the tank was full, but then when I reached about 100 bar it would stop.

I then didn't dive for a while and I didn't have the tools to have a look at it. When I dived again, it was fine. For about a week... Then the same thing happened. And then it was fine again. Until one day when the whistling was continuous (not just during inhalation), but it stopped when I reached about 100 bar. The next dive it was fine.

I then opened it and applied lots of silicone to the O-ring between the two plastic bushings (number 22 in the schematics). It still whistled (only during inhalation). I then asked a friend to buy me a service kit (my reg had all o-rings changed about 50 dives prior to this). I finally got the service kit and the tools I need to open it, so I replaced the O-ring (I made sure to use the one with the red stripe) and the plastic bushings holding the O-ring, put lots of Christolube, but it's still whistling!

One of my friends is telling me NOT to use the O-ring with the red stripe just to see if it makes a difference. I might try just to check if the whistling goes away.

One last remark, I applied lots of Christolube on the two O-rings at the base of the piston and on the white one on the piston stem. Oh, and I changed the main spring as well as the tech (also Scubapro certified) from a dive centre I went to told me it could be the cause.

If anyone has any idea how I could fix this it would be greatly appreciated.

I know many will say "Go to the nearest Scubapro Service centre". I'm on a small island on Borneo, the nearest service centre is over 1000 kilometres away...

Thanks

 

[redacted]

a friend had a similar problem with his Mk25. I replaced the SP o-ring (it felt too soft) with a generic -010 duro 90 and the problem seemed to be cured. I believe the SP o-ring is supposed to be duro 85 but know they have had some problems in the past with the o-ring being a bit on the soft side. a certain amount of tolerance is acceptable but they may have just slipped a bit to low

 

[Teller]

a friend had a similar problem with his Mk25. I replaced the SP o-ring (it felt too soft) with a generic -010 duro 90 and the problem seemed to be cured. I believe the SP o-ring is supposed to be duro 85 but know they have had some problems in the past with the o-ring being a bit on the soft side. a certain amount of tolerance is acceptable but they may have just slipped a bit to low

Thanks again for the help.

 

[Couv]

I agree with Master Awap regarding replacing the o-ring. However, before you do that here is a bit of gee-whizz information and a suggestion.

Have a very close look using a magnifying glass at your new duro 90 o-ring. See a small ridge around the inside and outside diameter? The tiny bit of material left over from the molding process is known as “flash” and usually causes no problems; but in a dynamic application it can remove lubricant from the surface it seals against much like a windshield wiper.

Remove the flash-particularly the bit around the I.D., with a bit of rolled up sandpaper (about 400 grit or finer) then rinse, dry, and lube the seal before installing it. This process will not only remove the flash, but will make tiny "potholes" on the sealing surface of the o-ring that will serve to hold lubricant.

If this doesn’t work, I have a little more radical suggestion for your next attempt.

Good luck and keep us posted.

Couv

 

[elan]

I had the same issue, lubricating the oring, turning the spring did not help, ditched the SP oring and put a poly 90 one and the issue disappeared.

a friend had a similar problem with his Mk25. I replaced the SP o-ring (it felt too soft) with a generic -010 duro 90 and the problem seemed to be cured. I believe the SP o-ring is supposed to be duro 85 but know they have had some problems in the past with the o-ring being a bit on the soft side. a certain amount of tolerance is acceptable but they may have just slipped a bit to low

 

[NozBzh]

Thanks a lot for the help.

I'll try to check this flash leftover, but I don't have sandpaper here... I'll see if I can get some on mainland Borneo when I go, it's a small town but they should have that.

I'll try using another O-ring from the SP service kit as my friend suggested (same size but without the red stripe).

I'd love to try one of these duro 90 O-rings but I have no idea where to buy one. Even if I was in France (my home country) I wouldn't know where to look for one. Any suggestion? Who would use that? A plumber? If I know which sort of shop would sell it I might at least have a (slim) chance to find one here!

Thanks again for the good info

 

[elan]

Thanks a lot for the help.

I'll try to check this flash leftover, but I don't have sandpaper here... I'll see if I can get some on mainland Borneo when I go, it's a small town but they should have that.

I'll try using another O-ring from the SP service kit as my friend suggested (same size but without the red stripe).

No Do NOT do that. The other -010 o-rings in the kit are duro 70 orings used for low pressure hoses. They are not suitable for high pressure application especially dynamic. They will be wearing out quicker and can eventually extrude resulting in gas loss from HP chamber to the ambient.

---------- Post added October 15th, 2013 at 08:39 AM ----------

Thanks a lot for the help.

I'll try to check this flash leftover, but I don't have sandpaper here... I'll see if I can get some on mainland Borneo when I go, it's a small town but they should have that.

I'll try using another O-ring from the SP service kit as my friend suggested (same size but without the red stripe).

I'd love to try one of these duro 90 O-rings but I have no idea where to buy one. Even if I was in France (my home country) I wouldn't know where to look for one. Any suggestion? Who would use that? A plumber? If I know which sort of shop would sell it I might at least have a (slim) chance to find one here!

How much is it to send an envelope to your place from Canada? I could possibly mail you a couple if it cost a couple of bucks to mail. PM me your address I will try to check.

 

[NozBzh]

Elan, I just saw your post. I tried using one the other 010 o-ring and it still whistled. I switched back to the one with the red stripe and of course it still whistles.

That would be great if you can send me one, I'll PM you now.

Thanks a lot

 

[halocline]

It's only whistling when you're inhaling, correct? Or continuously? If it's continuous, the next step is to pressurize the reg and submerge it in a tub or rinse tank so you can see if there are tiny bubbles coming out of the ambient chamber. If so, probably not a good idea to dive with it.

Usually the whistling is kind of like a harmonica, resulting from resonance in the piston shaft as air goes by the edge and causes vibrations. It's annoying but not dangerous. The idea behind the extra lube is that it dampens the vibrations, but you probably already know that.

 

[andrewy]

Make sure that plastic spacer installed right side up. wrong side has little notches , they leave marks on oring and make stag e whistle.

---------- Post added October 18th, 2013 at 11:19 PM ----------

space on high pressure side.