What was found
ON ARRIVAL, CREW REPORTED FUMES IN COCKPIT. F/A REPORTED SMELL IN AFT CABIN. A/C RETURNED TO MDW & LANDED W/O INCIDENT. REMOVED BELLY FAIRINGS FOR ACCESS TO LT PACK. INSPECTED PACK DUCTING & FOUND VASELINE ON DUCT SEALS & JOINTS. REMOVED WATER EXTRACTOR SEALS & JOINTS, REMOVED VASELINE, & RENSTALLED WATER EXTRACTOR. REMOVED DUCT BETWEEN MAIN HEAT EXCHANGER & ACM. CLEANED SEALS & JOINTS & REMOVED VASELINE. REINSTALLED DUCT. REMOVED ANTI-ICE VALVE/PRIMARY HEAT EXCHANGER BYPASS DUCT. CLEANED VASELINE FROM SEALS & JOINTS. REINSTALLED DUCT. REMOVED REHEATER DUCTING. CLEANED RESIDUE FROM SEALS & DUCTS. REINSTALLED REHEATER DUCTING. PERFORMED OPS CHECK OF LT PACK USING APU BLEED. OPS TEST NORMAL.