What was found
DURING THE FIRST FLIGHT SINCE ENG FLUSH, THE COCKPIT & CABIN FILLED WITH SMOKE. THE SMOKE WAS CONSISTENT WITH THE SMELL FROM RUNNING THE HEATER AFTER AN ENG FLUSH. INSPECTED BOTH ENGS FOR LEAKS & BURNED WIRING WITH NO DEFECTS NOTED. THIS WAS THE FIRST FLIGHT AFTER ENG & COMPRESSOR WASHES FOR EACH ENG. THEN GND RAN WHILE THE MX INSPECTED & FOUND EVIDENCE OF COMPRESSOR SOAP BURN OFF. THE ACFT WAS SHUT DOWN ONCE ALL OF THE SOAP RESIDUE HAD BEEN COMPLETELY BURNED OFF. PERFORMED A CHECK FLIGHT TO CONFIRM THE SMELL & SMOKE HAD DISSIPATED. AFTER SHUTDOWN VISUALLY INSPECTED ENGS & ENG COMPARTMENTS. NO LEAKS OR BURNED WIRING WERE FOUND. AT THIS TIME, THE ACFT WAS RETURNED BACK TO SERVICE.