What was found
AT CRUISE FL 340 REC'D L HYD QTY EICAS W/ QTY = .41 IN 5 1/2 MINUTES L HYD QTY WENT TO ZERO. IN ANOTHER 4 MIN L HYD PRESS BEGAN TO DROP. COMPLIED W/ QRH (TURNED "ON" L ELEC HYD PUMP) & PRESSURE RECOVERED. NEXT CAME EICAS L HYD PRIM PUMP. SECURED SAME PER QRH. SOON L HYD PRESS BEGAN TO DROP AGAIN & L HYD SYS MAINT STATUS MESSAGE CAME. L HYD PRESS WENT TO 30 PSI & SECURED L ELEC HYD PUMP PER QRH. TIGHTENED PLUG ON LT OTBD ELEVATOR PCA AND RE-SAFTIED REF AMM 27-31-05-4. PICTURES UPLOADED, PLUG IDENTIFIED WITH SAFETY WIRE. LEAK AND OP'S CK NORMAL. OK FOR SERVICE.