What was found
DURING A ROUTINE 100 HOUR INSPECTION, BLUE FUEL STAINING WAS FOUND ON THE TOP INTAKE SIDE OF THE NR 5 CYLINDER. CLOSER EXAMINATION REVEALED THAT THE CYLINDER WAS CRACKED, BETWEEN THE 14TH & 15TH COOLING FINS ON THE INTAKE SIDE OF THE CYLINDER HEAD INTO THE INTAKE PORT. THIS IS THE 7TH OCCURRENCE WE HAVE FOUND ON THIS SET OF ENGS IN 1833 HOURS SINCE A FACTORY OVERHAUL WITH ALL NEW OEM CYLINDERS. THE CYLINDER WAS REPLACED WITH NEW & BOTH THE MFG & THE FAA ARE INVESTIGATING. MFG SI 1553 ADDRESSES CRACKS IN THIS AREA & RECOMMENDS INSTALLING A CYLINDER FIN STABILIZER TO PREVENT THEM, HOWEVER THIS ENG WAS BUILT AFTER THAT SI WAS ISSUED & WAS NOT EQUIPPED WITH STABILIZERS, NOR DO NEW CYLINDERS COME OUTFITTED WITH THE STABILIZERS.