What was found
AT ABOUT 100 MILES OUT FROM LANDING THE AIRCRAFT, PRODUCED SMOKE IN THE COCKPIT. ALSO NOTICED THE LOSS OF THE RT HYDRAULIC SYSTEM AS QUANTITY WENT TO ZERO ACCOMPANIED BY 'R HYD PRES LOW' LIGHT. FLIGHT CREW DECLARED AN EMERGENCY, REQUESTED CFR, AND LANDED UNEVENTFULLY AT MCO. CREW SUSPECTED THAT THE APU WAS INGESTING THE LEAKING HYDRAULIC FLUID CAUSING SMOKE. MAINTENANCE REPLACED A FAILED VACUUM BREAKER RELIEF VALVE, RT ENGINE HYDRAULIC PUMP AND FILTERS, AND BOTH WATER COALESCER BAGS. SERVICED AND LEAK CHECK OK. AIRCRAFT RETURNED TO REVENUE FLIGHT.