What was found
WHILE REPAIRING AN UNRELATED ITEM, THE MECHANIC NOTICED A CRACK APPROXIMATELY ONE INCH LONG (RUNNING TOP TO BOTTOM) ASSOCIATED WITH THE MOST FORWARD UPPER THROUGH-STUD ON THE NR 4 CYLINDER. THE CASE WAS INSPECTED IAW TCM SB M90-17 AND DETERMINED TO BE UNAIRWORTHY BY THE LOCATION OF THE CRACK. THE CASE HAD BEEN REPAIRED AT SOME TIME IN THE PAST IN LOCATION OF THE CRACK. SUBMITTER SUGGESTED A POSSIBLE CAUSE FOR THE CRACK COULD BE FROM STRESS CAUSED BY THE REPAIR OR POSSIBLY IMPROPER HEAT TREATING TO THE SURROUNDING AREA OF REPAIR.