What was found
(LOG 5814032) UPON ARRIVAL, AFTER TRANSFER OF A/C PACKS OVER TO APU WE NOTICED A ODOR OF BURNING SMELL IN THE COCKPIT. NO ODOR NOTICED UPON ARRIVAL. PERFORMED B737 FIM 21-00 TASK 806, FUMES IN COCKPIT POSSIBLY FROM APU PER CREW. LOAD COMPRESSOR ALL NORMAL, DUCTS NORMAL NO CONTAMINATION. ONLY NOTICED OLD DE-ICING FLUID IN TAIL AREA. VISUAL INSPECTION OF BOTH PACK BAYS NORMAL, ENGINE INSPECTIONS NORMAL PER B737 AMM 21-00 & 71-00. PERFORMED OIL CONTAMINATION REMOVAL OF A/C AND PNEUMATIC SYSTEMS PER B737 AMM 21-00-01-100-801. ALL ENG RUNS, APU RUNS, PACK OK.