As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING ENGINE CHANGE, THE ENGINE MOUNT WAS REMOVED FOR INSPECTION. MOUNT WAS REMOVED FOR INSPECTION. THE FIREWALL ATTACH POINTS FOR THE ENGINE MOUNT WERE THEN INSPECTED. THE UPPER LEFT BRACKET WAS FOUND CRACKED AT THE ENGINE MOUNT BOLT HOLE. THE BRACKET INBOARD 2 RIVETS THAT ATTACH IT TO THE LONGERON HOT SECTION WERE MISSING. SUSPECT THIS CAUSED THE CRACK.