As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
TO COMPLY WITH SB 518C. A NEW THERMOSTATIC BYPASS VALVE WAS INSTALLED. DURING RUN-UP TEST, THE NEW VALVE FAILED TO CONTROL OIL TEMPERATURE. THE VALVE WAS RETURNED TO VENDOR AND ANOTHER NEW ONE WAS INSTALLED AND FUNCTIONED SATISFACTORY.