What was found
ELECTRICAL OVERHEAT SMELL IN COCKPIT DESCENDING THRU 24,000 FT, NO SMOKE. SMELL DISSIPATED, THEN RETURNED ON ADDING POWER LATER IN DESCENT. *S/D* FOUND OIL RESIDUE ON NR 1 ACM. REPLACED ACM, NO OIL LEAKS FOUND. INVESTIGATION REVEALED ACM INGESTED FOD, NO DAMAGE FOUND, THE OIL SEALS WERE INTACT. A 2ND ACM WAS REMOVED ON 5/3. THE ACM WAS DISASSEMBLED AND TESTED, NO LEAKS FOUND. ACM'S WERE NOT THE CAUSE OF THE SMELL. THE NR 2 MAIN ENG WAS REPLACED. AFTER REPLACEMENT OF 2 ACMS, 2 PACK BURNOUTS, SMELL STILL EXISTED, AFTER NR 2 ENGINE REPLACEMENT THE OIL SMELL DISAPPEARED. THE NR 2 ENGINE WAS LIKELY THE CAUSE OF THE OIL SMELL.