What was found
DURING PREFLIGHT INSPECTION, FLIGHT CREW NOTICED HYDRAULIC FLUID ON BELLY OF ACFT. MX DISCOVERED A .8750 INCH CRACK ON THE HYD LINE THAT CONNECTS MAIN SYS RETURN FILTER & HYD RESERVOIR (RETURN SIDE). COULD NOT DETERMINE THE CAUSE OF DEFECT, ALL SUPPORTING CLAMPS IN PLACE & IN GOOD CONDITION. NUTS ON EACH END OF LINE PROPERLY TORQUED, NO INTERFERENCE OR TOUCHING OF ANY PART OF ACFT & AFFECTED LINE, NO CORROSION PRESENT. CRACK LOCATED ON INTERMEDIATE RADIUS, OF THIRD BEND FROM FILTER HOUSING. CRACK RAN LATTERLY ON BOTTOM SIDE OF TUBE.