What was found
AIRCRAFT RETURNED TO DEPARTURE DUE TO Y RESERVOIR LOW LEVEL. DURING INITIAL INSPECTION, FOUND LEAK COMING FROM FITTING ON DUAL DISTRIBUTION BRAKE VALVE BRAKE PRESSURE LINE. FOUND DETERIORATED O-RING R & R O-RING IAW MM 32-43-14. SERVICED YELLOW SYSTEM IAW MM 12-12-00 AND BLEED YELLOW SYS HYD IAW MM 29-00-00-870-004. ALSO, INSPECTED YELLOW SYS FILTER DPI'S, ALL WERE FOUND OK. SYS WAS NOT DEPLETED OPERATION AND LEAK CHECK NORMAL.