What was found
GOT A "L HYD QTY" EICAS MESSAGE APROXIMATELY 2.5 HOURS INTO FLIGHT. L HYD QTY WAS .46 ON STATUS PAGE WITH RF MAGENTA. ALSO HAD "QTY" LIGHT ON OVERHEAD. HYD QTY .07 ON SHUTDOWN. FLIGHT CREW VERBALLY RELAYED TO ACMX THAT THE LEFT HYDRAULICS NEVER LOST PRESSURE OR FULL QTY. FOUND LT ELEV (FAR LEFT PCU) LEAKING FROM BLUE PLUG TEST PORT, RUPTURED O-RING FOUND (SEE PICTURES). REPLACED O-RING PER CMM 27-30-07 ITEM 390, OPS AND LEAK CHECK SAT PER AMM 27-31-00-5 (ELEV CHECK OPS) & 29-11-00-6 (HYD LEAK RATE).