What was found
SYSTEM B HYDRAULIC FAILURE: STARTED WITH SYSTEM B ENG 2 LOW PRESSURE LITE - DID QRH FOR THAT - HYDRAULIC QTY % WENT DOWNT TO 8%, PRESSURE STAYED AT 2900 STARTED AROUND CLIMB OUT 25000 FT. GROUNDED - YES. AIR TURNBACK - DIVERSION TIME 25 MINUTES - REMOVED AND REPLACED #2 ENG HYDRAULIC EDP REF B737-900 AMM 29-11-11. FLUSHED THE B SYSTEM, REF AMM 29-11-00. REMOVED AND REPLACED THE EDP CASE DRAIN FILTER, PRESSURE MODULE FILTER, RETURN MODULE FILTER AND PTU PRESSURE FILTER. NO DEFECTS NOTED, LEAK CHECK GOOD. REF AMM 29-11-51, AMM 29-11-71, AMM 29-11-61 AND AMM 29-22-21.