What was found
STRONG ODOR OF EXHAUST EXPERIENCED DURING CRUISE FLIGHT. TURNED THE BLEED SOURCE TO THE LEFT SIDE ONLY AND THE ODOR WENT AWAY. AFTER 10 MINUTES, PUT THE BLEED SOURCE ON THE RIGHT SIDE AND THE ODOR RETURNED. BORESCOPED FRONT CORE OF ENGINE AND REAR TURBINE SECTION. REMOVED BOV AND BORESCOPED COMPRESSOR AREA WITH NO DISCREPANCIES FOUND AT THIS TIME. REMOVED NOSE CONE AND INSPECTED FANSHAFT AND FOUND NO OIL PRESENT. REINSTALLED NOSE CONE. PERFORMED ENGINE GROUND RUNS AND COULD NOT DUPLICATE THE DISCREPANCY. ALL WORK PERFORMED IAW MM71-00, 72-00, AND 75-30.