What was found
SUSPECT HIGH ENGINE OIL CONSUMPTION OF NR 1 ENGINE ( ENGINE CHANGED PRIOR DAY). ACFT GROUNDED. COMPLIED WITH AMM 79-00-00, EXTERNAL OIL SYSTEM INSPECTION AND FOUND NO EXTERNAL OIL LEAKAGE AT THIS TIME. EXAMINED THE AFT SUMP OIL SYSTEM FOR LEAKAGE IAW AMM 79-00-00 AND FOUND NO LEAKAGE AT THIS TIME. OPENED ENGINE COWLS IAW AMM 71-11-00 AND FOUND NO OBVIOUS LEAKS AT THIS TIME. DRAINED NR 1 ENGINE AGB AND MAIN OIL TANK IAW AMM 12-13-11, LESS THAN 2 QUARTS DRAINED FROM THE AGB. FOR TROUBLESHOOTING PURPOSES, CHECKED SCAVENGE SCREW AND FOUND EXCESSIVE UNIDENTIFIED MATERIAL FROM THE AFT NR 3 SCREEN, CHECKED SCAVENGE SCREENS IAW AMM 79-00-00, ALL PREVIOUS MAINTENANCE PERFORMED IAW FIM 79-05 TASK 801. REMOVED AND REPLACED THE NR 1 ENGINE IAW T/C 78471000 AND 78471001.