What was found
AFTER GEAR AND FLAP RETRACTION L HYD QTY MSG FOLLOWED BY L HYD SYS PRESS MSG/LIGHT. FOLLOWED QRH AND CONTACTED DISP/MX. L SYS QTY REMAINED AT 0.00 L HYD SYS PRESSURE REMAINED NORMAL 3200PSI AFTER WE PUT GEAR DOWN THE TU FAILED WENT AROUND AND COMPLETED QRH PROCEDURES. FOUND DPI MISSING INDICATOR ON LT EDP PRESS AND CASE DRAIN MODULE CAUSING HYD LOSS. REPLACED SAME PER AMM 29-11. NEEDS LK CK. REMOVED BOTH FILTERS FROM CASE DAIN MODULE LT PYLON NEEDS NEW ONES. INSTALLED AND CW LK CK. R&R PTU PER AMM 29-22.