two new seals, no luck. Could probably have cleaned groove better. I have thought of leak from another location but really appears from puck. I will try to clean groove though.
Its only a few places: Input line, bleeder valve or the piston seal.
I haven't finished mine yet and they weren't leaking. But they wouldn't retract. I disassembled them and the new seals (Square cross section O Rings) wern't the right size! See if your new ones fit snug to the piston first, then install.
I used the soft bristle brush with my Dremel to clean the grooves.