What was found
DURING DESCENT THROUGH 9000 FEET, BOTH PILOTS NOTICED STRONG, EXHAUST SMELL IN THE COCKPIT. ENVIRONMENTAL WERE TRANSFERRED TO THE APU, WHICH MINIMIZED THE SMELL MOMENTARILY. THE SMELL WAS CLOSER TO EXHAUST, NOT DEICING FLUID, NOT ACRID, OR ELECTRICAL. CORRECTIVE ACTION: REMOVED INTERNALLY LEAKING APU P/N 3800774-2 S/N P-847 AND INSTALLED CUSTOMER SUPPLIED INSPECTED APU P/N 3800774-2 S/N P-803. PERFORMED GOOD OPS AND LEAK CHECK. WORK PERFORMED REF CL-350 AMM 49-11-00 AND 49-11-01