What was found
ON MAINTENANCE POST-FLIGHT, DISCOVERED RT ENGINE HYDRAULIC MAIN FILTER WET WITH HYDRAULIC FLUID. INVESTIGATION SHOWED LEAKAGE FROM FILTER BOWL SEAL AND TEFLON CHEVRON AREA. INSPECTION OF O-RING SEAL AND BACK-UP TEFLON RINGS SHOWED BEVEL DEFECT ON BACK-UP RING LETTING O-RING DEFORM. THE BACK-UP RING SHOWED BEVELS CUT THE SAME ANGLE PREVENTING OVERLAP FOR A SMOOTH SURFACE. REPLACED O-RING AND BACK-UP RINGS THAT CORRECTED THE CONDITION. RECOMMEND TECHNICIAN'S ATTENTION TO BACK-UP RING INSPECTION AT TIME OF INSTALLATION.