The hydraulic piston/cylinder is the blade tensioner on a wood milling bandsaw but I'm posting it in this forum since it may have some similarity to an automotive brake master cylinder.

Th situation is the master cylinder is adjusted manually with a screw ram just prior to milling to establish a hydraulic pressure of about 2000 psi on a master and in turn a slave cylinder which moves one of the wheels to tension the blade.

The master piston is the shiny slug in the pic below and it fits inside the master cylinder as per long red arrow.
The piece on the right caps the master cylinder and has an internal fine thread into which screw ram is located which also makes contact with the slug which pushes on hydro fluid etc.
A hydro line then goes out the back of the master to the slave ram (R) which tensions the blade


Lately the pressure has not been holding dropping about 100 PSI every minute or so which is consistent with a very slow oil leak from the screws ram.

I thought it might have a damaged O-Ring but when (after a great effort) I pulled it apart, it has no O-ring and am wondering what one does at this point in this sort of repair?

To get the two halves of the master cylinder apart was no fun as I had to heat it up and use a pipe wrench with a cheater bar - turned out it was also Loctited on! HARD!
First thing was I had to take the gauge at G off and let the oil dribble out
Then to make sure I wasn't going to melt any O-ring with the heat I had to drive the internal piston up to the top of the cylinder which I did with a 6mm diam length of steel bar.
At first piston didn't move so I leaned over the cylinder and pushed harder and when it did move all of sudden a jet of residual oil shot out of G and hit me between the eyes.
I had glasses on but hydro still got into my right eye, hair etc.

Any idea much appreciated.
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