Our refrigeration technician returned to a Dinuba CA customer to continue troubleshooting a walk-in cooler that had overheated and had a bad piercing valve. After replacing the valve, our technician tested all components and determined that the compressor had failed, with multiple leaks detected possibly in the evaporator coil. Shut down system, charging with nitrogen to continue leak search. Will need to replace the compressor, liquid line drier and install service ports. Recommend adding dye to the system to pinpoint remaining leak locations for repair.