What was found
HYDRAULIC FLUID QUANTITY INDICATING SYSTEM READS ZERO. HYD QTY LIGHT ON. EICAS MESSAGE DISPLAYED C HYD QUANTITY. LOW PRESSURE LIGHT IS ON. AIRCRAFT DIVERTED TO JFK AND LANDED WITHOUT FURTHER INCIDENCE. AIRCRAFT WAS GROUNDED BY MAINTENANCE. MAINTENANCE FOUND SPOILER PCA NO.10 LEAKING, R&R'D NO.10 PCA PER AMM 27-61-02. OPS CHK NORMAL. SERVICED HYD SYSTEM PER AMM 12-12-01. OPERATED ALL FLIGHT CONTROLS OK, NO LEAKS NOTED. A/C REMAINS ETOPS 180. AICRAFT RETURNED TO SERVICE.