Remove the TSC union and remove the 8-32 socket-head cap screws that hold the union together . Use a Philips screwdriver or allen wrench to gently push the piston out of the housing.
Remove the cup seal and the O-ring . Clean the piston  to remove coolant, grease, and/or debris. Lightly grease the new O-ring and cup seal  with silicone grease and carefully install them onto the piston.
Before re-inserting the piston into the housing, clean the inside of the housing. Apply generous silicone grease around the large OD of the piston  and on the large tapered surface of the piston. Align the anti-rotation pins and reinsert the piston into the housing.