What was found
WHILE OPERATING RT PACK IN MANUAL WITH MIX VALVE AT HALF POSITION, THE RIGHT PACK TEMP WENT TO 150 DEGREES AND WAS ACCOMPANIED BY CABIN SMOKE DURING DESCENT INTO EWR. THE SMOKE CLEARED WHEN COOLING DOOR WAS OPENED AND MIX VALVE WAS ADJUSTED. THE AIRCRAFT LANDED AT EWR WITHOUT FURTHER PROBLEM. MAINTENANCE CHECKED THE OPERATION OF BOTH PACKS ON THE GROUND WITH ENGINES RUNNING AND WERE UNABLE TO DUPLICATE THE PROBLEM. THE ENGINE BLEED AIR DISTRIBUTION WAS ALSO CHECKED IAW MM 36-10-0 AND ALL OPERATION CHECKED GOOD.