As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PHL - FLT 126 - APPROXIMATELY FORTY MINUTES OUT OF PHL, THE CREW RECEIVED THE E/M 'L BLD OVHT'. CREW CLOSED THE LEFT BLEED AND SECURED THE LEFT PACK. FLIGHT RETURNED TO PHL AND LANDED WITH NO FURTHER INCIDENT. MAINTENANCE REPLACED THE LEFT ENGINE PRECOOLER. (M)