What was found
FUEL LEAKING FROM "B" NUT OF SERVO FUEL SUPPLY LINE TO THE BACK SIDE OF IDG AIR-OIL HEAT EXCHANGER. LINE IS TAGGED. SAFETY WIRE REMOVED FROM "B" NUTS OF THE SERVO FUEL RETURN AND SUPPLY LINES TO THE BACK SIDE OF AIR-OIL HEAT EXCHANGER. TIGHTENED "B" NUT TWICE AND NO HELP. ACP'D ENGINE RUN MESSAGE STILL RETURNS FAULT IDG VALVE. STARTED REMOVAL OF IDG HEAT EXCHANGER AND VALVE. REPLACED IDG-AIR OIL COOLER. OPS AND LEAK CHECK OKAY. INSTALLED NR 2 IDG AIR OIL HEAT EXCHANGER, PERFORMED 5 MINUTE IDLE NO LEAKS NO MESSAGES.