What was found
DURING CLIMB, FLIGHT 850 (MDE-VCP), LEFT HYD QTY DECREASED TO ZERO AND SYSTEM PRESS & QTY LIGHTS ILLUM EICAS MSG L HYD SYS PRESS & LEFT HYD QTY DISPLAYED. RETURNED TO MEDELLIN. FOUND HYDRAULIC LEAK BY PCA SPOILER CAP FILTER. RIGHT NOW THE AIRPLANE IS OUT OF OPERATION UNDER MAINTENANCE INSPECTIONS. REMOVED AND REPLACED O-RINGS & RETAINER BACKUP RINGS ON PCA SPOILER CAP FILTER IAW AMM 27-61-02 PAGE 402, PERFORMED CHECKS IAW AMM 27-61-02 PAGE 420 WITH SATISFACTORY RESULTS. OVERWEIGHT LANDING INSPECTION PHASE I WAS PERFORMED IAW AMM 05-51-35 PAGE 202. NO DAMAGES FOUND. RETURNED TO COMMERCIAL OPERATION.