What was found
PILOT REPORTED, AFTER FLAP RETRACTION THEY LOST HYDRAULIC FLUID. PROPER CHECKLIST ACCOMPLISHED, DISCUSSED OPTIONS, COORDINATED WITH FLIGHT CONTROL AND CONTINUED TO OAKLAND. PILOT DECLARED EMERGENCY WITH BAY APPROACH AS A PRECAUTION. EXTENDED GEAR MANUALLY AND WAS ABLE TO GET APPROACH FLAPS, LANDING FLAPS AND LANDED NORMALLY. MAINTENANCE RESEALED THE SLOT CHECK VALVE, RESERVICED SYSTEM LEAK AND OPS CHECK GOOD ON A 20 MIN ENGINE RUN. CYCLED AILERONS RUDDER AND FLAPS NUMEROUS TIMES AND NO LEAKS NOTED.