What was found
PDX - FLIGHT 2310 - FLAP POWER CAUTION. CREW ABORTED LANDING DUE TO THE FLAPS REMAINING UP WHEN SELECTED TO 5 DEGREES. THE FLAP CONTROL CIRCUIT BREAKER WAS RESET IAW THE EMERGENCY CHECKLIST. THE FLAP POWER CAUTION CAME BACK AND THE FLIGHT MADE A ZERO FLAP LANDING. MAINTENANCE INTERROGATED CDS AND FOUND A LOSS OF HYDRAULIC POWER FAULT. MAINTENANCE REMOVED AND REPLACED THE FLAP POWER UNIT PER Q400 MM TASKS 27-52-01-000-801 AND 27-52-01-400-801. MAINTENANCE PERFORMED A FUNCTIONAL TEST OF THE FLAP DRIVE SYSTEM. FUNCTIONAL CHECK AND LEAK CHECK GOOD. NO FURTHER DETECTS NOTED.