Abstract: The liner retainer assembly includes a cylinder that is mounted on a module of the fluid end of a pump. The cylinder has an aperture for receiving a liner and a retaining piston. A retaining nut is secured on the end of the retaining piston and engages one end of the liner. The retaining piston forms a fluid cavity and a spring cavity within the cylinder. The spring cavity houses a plurality of springs which bias the piston, retaining member, and liner towards the module, thus providing a resilient securing force. The fluid cavity communicates with a supply of hydraulic fluid for biasing the piston away from the module to relieve the springs. By pressurizing the fluid cavity, the springs are compressed to disengage the retaining member from the liner and allow the unthreading of the retaining member and then the removal of the liner.