Mk 25 honking/ howling noise from 1st stage help

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Most likely the piston shaft or piston head o-rings are damaged. The shaft o-ring can easily get damaged if a piston bullet is not used when the piston is installed.
MK25 piston head and shaft o-rings.PNG
 
Yes I did submerge it the air was coming out of the ambient chamber holes as suspected. I checked the ip and it was right at 125psi and locked up tight. However I was starting to do the tear down and I noticed that the chamber body was very loose. So loose in fact that I was able to get almost 4 full turns on it. I thought this might have contributed to the issue but it did not fix it. So I repacked the the two O-rings in the pack and it did not fix the issue. I am starting to lean toward the high pressure oring as the possible culprit.
 

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  • MK20-MK25RepairGuide.pdf
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  • MK25 AF rev D-V5.pdf
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Scubapro piston regs have had a tendency to honk at least since I bought my first Mk10 back in 1988.
If it honks - it's a Scubapro.
But, the damn things always work, which is usually more important than the stealth qualities of the reg.
Fortunately, the 9 Mk20s that I have don't honk.

Michael
 
My MK-17 never honked.... :poke:
 
@couv you hit the nail on the head it was indeed the piston shaft oring. A big thanks to you and everyone else for all of the pointers and help.
 
@couv - where did you get that colored image?
 
https://www.shearwater.com/products/peregrine/

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