As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) HIGH OIL TEMPERATURE ON NUMBER 1 ENGINE. TEMP REACHED 108 DEG C. CREW FOLLOWED QRH PROCEDURES AND CONDUCTED AN AIR RETURN TO BASE. LINE MAINTENANCE INVESTIGATION IDENTIFIED THE PROBABLE CAUSE OF THE DEFECT TO BE FAILURE OF THE OIL COOLER BYPASS VALVE. VALVE ASSEMBLY REPLACED & FOLLOWING APPROPRIATE GROUND CHECKS IN ACCORDANCE WITH THE AIRCRAFT`S MAINTENANCE MANUAL THE AIRCRAFT WAS RETURNED TO SERVICE WITHOUT FURTHER INCIDENT.