What was found
SMOKE ENTERED CABIN WHILE EN ROUTE. THE NR 3 PNEUMATIC SUPPLY AND NR 3 AIR CONDITIONING PACK WERE SHUTDOWN IAW CHECKLIST AND THE SMOKE CEASED. THE FLIGHT CONTINUED TO IAH WITHOUT FURTHER PROBLEM. MAINTENANCE REPLACED THE NR 3 PACK COALESCER BAG. THE PACK WAS RUN WHILE OPERATING THE NR 3 ENGINE AND APU AND OPERATION CHECKED GOOD WITH NO SMOKE NOTED. THE AIRCRAFT COMPLETED FIVE FLIGHTS WITHOUT REPORTS OF CABIN SMOKE SINCE THIS CORRECTIVE ACTION WAS IMPLEMENTED.