What was found
CENTER TANK WENT FROM 300 INDICATED TO 1200 IN IST 1.5 HOURS OF FLIGHT. WHEN MAINS BELOW HALF, SCAVENGED BACK TO ZERO. *S/D* THIS PROBLEM WAS CAUSED BY TWO MINOR LEAKS TO THE CENTER FUEL TANKS. ONE WAS A LEAKY COUPLING ON THE FUEL SCAVENGE PLUMBING IN THE CENTER TANK. THE O-RING WAS REPLACED AND THE COUPLING WAS RESECURED AND SAFETIED. THE SECOND WAS CAUSED BY A DAMAGED RT SURGE TANK DRAIN LINE. THE DAMAGE WAS LOCATED ON TUBE ASSY PN 343T0012-3 LOCATED JUST OUTBOARD OF RIB 3. THE DAMAGE TO THE TUBE WAS CAUSED FROM CONTACT WITH A HI-LOK COLLAR ON AN ADJACENT STRINGER. THE TUBE WAS REPAIRED PER GN/MM7-0-4-9.