What was found
(CAN) HYD SYSTEM 2 QTY DEPLEATED TO 1 IN FLIGHT. RUDDER ISO C/M.RETURNING TO YVR. (RESOLVED ON W/O: 265192 TASKCARD: NR-00001) FOUND L/H MAIN LANDING GEAR SOLENOID SEQUENCE VALVE LEAKING. SEQUENCE VALE REPLACED IAW DHC-8 32-10-51. MAINT IRREGULARITY REPORT. AIRCRAFT DEPARTED YVR,GEAR SELECTED UP. TWO SECONDS LATER RUDDER ISO LIGHT CAME ON. MOST OF HYD FLUID DEPARTED. GEAR WOULDN`T COME UP. FOR SAFETY, PILOTS DID ALTERNATE SELECTION DOWN.A/C RETURNED TO YVR HANGAR.IT WAS FOUND THAT THE TOP(SOLENOID) OF THE VALVE ALMOST FELL OFF. TWO SCREWS HAD SHEARED HAD SHEARED OFF.IN TURN LETTING THE HYD FLUID NR 2 SYSTEM TO LEAK OUT.