SP MK 25 IP

[halocline]

A leak into the ambient chamber is almost always a leak at the HP o-ring on the piston shaft, much less often from the piston head o-ring. But….there is that internal o-ring in the MK25 piston I mentioned. There are ways of determining which is the leaker, but my guess with your IP creep and noise, you just need a rebuild by a competent technician and that will fix all the problems.

 

[Johnsonsa93]

A leak into the ambient chamber is almost always a leak at the HP o-ring on the piston shaft, much less often from the piston head o-ring

The only time I see a leak at the HP o-ring is if someone forgot to use a piston bullet to install the piston and damaged the HP o-ring or if someone somehow scratched the shaft of piston which I would imagine is more difficult than damaging the tip.

Almost all ambient chamber leaks I see on flow through piston desings like the MK25 & the Atomics is from the piston head o-ring. Generally it's from corrosion build up when someone does a poor job cleaning the ambient chamber out or if someone gets debris stuck on the piston head o-ring. Where I work we have lots of black lava rock sand which is harder than brass. That lava rock sand will get stuck right on the piston head o-ring and as the piston cycles up and down it will wear a nice little grove into the metal.

Pictures attached

 

[Mobulai]

The whine / squeal can be fixed by 1) cutting the bushings 2) rotate the seat 90 degrees and 3) flipping the springs. Those tips are from a SP technical bulletin

the leak from the ambient chamber could possibly be from damage to the metal of the 1st stage body where the piston head o-ring seals against the body. Also possible if the piston shaft o-ring is damaged it could be from there. If the sealing surface for the piston head o-ring is damaged you'll need to replace the cap ( p/n: 107.13.012) that connects between the body and the swivel turret.

It's worth mentioning that if you have an IP creep AND an ambient chamber leak (if it's from the piston head o-ring) then your creep is worse than you think it is. Strong chance the piston will need to be replaced if this is the case.

So I finally got to open it up, I started by looking at the piston blunt nose after uncapping, just by eye I could spot 2 glistens of light that seemed like bumps..

I then go on taking out the seat, rings and piston shaft oring, under all the caked dry cristo and to my surprise.. only one out of the 2 rings came out, and the piston oring had a score mark so perfect it looked like a lp seat

I don’t know how on the 1st test pressurized it had a „slow“ creep, that thing should have shot up like crazy without the top ring (#15 on schematics), but maybe that scored oring helped relief some of that IP to the ambient chamber as you guessed @Johnsonsa93 , just in the weirdest possible variation

the cap looked very clean, but along with the piston head were very sticky, almost tacky, the piston orings also seemed to to be in shape

I’m glad whoever sold it to me didn’t have a burst hose or something equally horrible and lived to (not) tell (me) about it.. I am lost in the sauce so I move on

Time to break the micromesh and try my hand at this awesome guide by @rsingler buried at the bottom of my bookmarks , the only time I did something similar was on an mk10 sharp knife edge — ending with a low but acceptable IP (need to find me a shim), but I’m fairly optimistic about getting it to lock up, easier to dress and raise ip given the smooth edge and adjust screw