What was found
(CAN) ON PUSH BACK, A LEAK IN THE YELLOW HYD SYS OCCURRED WHICH RESULTED IN APPROX 15 LTRS OF HYD FLUID LEAKING ONTO THE RAMP AT GATE 18. THE CAA WAS NOTIFIED AT 0720 AND RAMP CLEANED UP SPILL IMMEDIATELY. YELLOW SYS PRESSURE LINE AND CHECK VALVE REPLACED AT PRESSURE MODULE AND BOTH YELLOW PRESSURE AND RETURN FILTERS REPLACED ALL IAW AMM 20-23-11-300-004 AND 29-13-45-610-001 AND 29-13-44-610-001. SYS CHECKED NORMAL.