What was found
(CAN) DURING ROUTINE MAINTENANCE THE ENGINE MOUNT RING (HORSE COLLAR) WAS FOUND CRACKED AT 2 OF THE 4 CORNERS, INSIDE JOINT. DUE TO THIS BEING A KNOWN PROBLEM, AN ADDITIONAL TASK CARD TO CHECK FOR THIS CONDITION, INITIATED IN 1999, WAS ADDED TO OUR MAINTENANCE SCHEDULE EVERY 100 HOURS. AS A RESULT, WE HAVE DISCOVERED THE CONDITION ON 12 SEPARATE COLLARS. THE COLLAR WAS REPLACED AND THE AIRCRAFT REL EASED.