What was found
ON DEPARTURE, #3 HYD SYSTEM CAUTION DURING GEAR RETRACTION. THEY DECLARED AN EMERGENCY, RETURNED TO CLT AND LANDED WITHOUT ISSUES IN CLT. THEY WERE NOT OVERWEIGHT ON LANDING. RTF-UPON SELECTED GEAR UP AFTER ROTATION HYD PUMP 3A AMBER CAS. FOLLOWED BY INBD GRND SPOILERS AMBER CAS AND GEAR DISAGREE. (NOSE FLAGGED RED) / SERVICED HYD 3 RESERVOIR IAW CRJ 900 AMM 12-12-29-611-802. FOUND FLUID QUANTITY TO HAVE A DIFFERENCE OF 35% WHEN PRESSURIZED VS NOT PRESSURIZED. BLED HYD 3 SYSTEM IAW CRJ 900 29-10-00-870-802. SYSTEM FOUND TO HAVE A CONTINUOUS AIR LEAK. REMOVED AND REPLACED HYD SYSTEM 3 BOOTSTRAP BALANCED RELIEF VALVE AND HYD SYSTEM 3 HYDRAULIC FLUID RESERVOIR. HYDRAULIC FLUID LEVELS NOW NORMAL AND AIR WAS PURGED FROM THE SYSTEM. PERFORMED EXTENSION/RETRACTION OF THE LANDING GEAR IAW CRJ 900 AMM 32-30-00-865-801. GEAR WAS SWUNG APPROXIMATELY 10 TIMES. NO FAULTS OR CAUTION MESSAGES APPEARED AND HYD LEVELS STAYED NORMAL. ALL OPS CHECK GOOD AT THIS TIME