As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: GRINDING NOISE HEARD FROM RADOME AREA FOLLOWED BY WEATHER RADARSYS L+R FAULT. DECESION MADE TO RETURN TO PHL, EMERGENCY DECLARED AND AIRCRAFT LANDED OVERWEIGHT WITHOUT INCIDENT. MAINTENANCE NEW RADAR DRIVE UNIT INSTALLED PER AMM B787-A-34-42-03-00A-720-A.