Shoebox 4500psi in need of assistance

I had a very similar issue with my f10. I posted about it here:


I see some photos are missing there. Sorry about that!

For my issue it was one very small oring that was behind the vent knob. If I can find the oring measurements I'll post them here!
 
It could be coming from the above suggestion, or the Burst Disc #27, or the Vent Valve Assembly #37. O-Rings will fix all but the Burst Disc.
I believe that the O-Rings for those parts are the same as the ones for the small check valve. The Vent Valve Assembly is underneath a flat metal plate with 2 small screws holding it down. Use caution when opening as the Assembly is spring loaded.
I have highlighted those parts on the attachment sheet for you to better see their locations.
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View attachment Shoebox Exp View I.pdf