What was found
SHIP 687 ACFT EMITS RANCID SMELL OF BURNING DIRT/PLASTIC THROUGHOUT ACFT. WORST BY DOORS. MIGHT GET WORST W/ LEFT PACK SW MOVEMENT. NEVER REALLY WENT AWAY. CORRECTIVE ACTION: RAN PACKS INDIVIDUALLY FOR EXTENDED PERIOD OF TIME. RAN BOTH ENG INDIVIDUALLY WIHT AND WITHOUT PACKS, INSPECTED ALL GALLEY COFFEE MAKER+ OVENS, INSPECTED FIRST CLASS PED SYSTEM AND INSPECTED C/B PANELS IN COCKPIT WITH NO DEFECTS AND NO SMELL IN REF W/ B757 FIM 21-00-01/301. REMOVED 14TH STAGE DUCTING AND PRE-COOLER DUCITNG ON NUMBER 1 ENGINE AND FOUND RESIDUE/BURNT REMAINS OF PLASTIC SUBSTANCE. REMOVED NBR 1 ENG PRE-COOLER ASSY AND VALVE IN REF W/ B757 AMM 36-11-15. S.D 873744. INSTALLED PRE-COOLER PER B757 AMM 36-11. NO LEAKS NOTED AT THIS TIME. RAN ENG AND TUNRED ON PACKS, FOUND NO PRESENCE OF BURNT SMELL.