As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CRUISE CREW RECEIVED A NR 1 BLEED LEAK EICAS MESSAGE DURING FLIGHT. CREW PERFORMED QRH, MESSAGE EXTINGUISHED. FLIGHT RETURNED TO DEPARTURE DUE TO ICING CONDITIONS ENROUTE. NO EMERGENCY DECLARED. MAINTENANCE FOUND THE AFT PRECOOLER GASKET RUPTURED. REPLACED AFT PRECOOLER GASKET IAW AMM 36-11-08, OPS CHECKED GOOD.