A tube-fitting assembly includes a formed tube, first and second threaded fitting members, and a sealing member. The tube has a first annular bead near an end of the tube and a second annular bead outboard of the first annular bead. The first threaded fitting member surrounds the tube and has a radially inwardly extending first shoulder inboard of the first and second annular beads. The second threaded fitting member has an annular second shoulder at an acute angle to a longitudinal axis of the tube. The second fitting member surrounds the end of the tube and is in threaded engagement with the second threaded member such that the second shoulder engages an outboard side of the second bead to establish a first seal between the tube and the second fitting member against leakage of fluid pressure. The sealing member is a washer or O-ring which surrounds the tube and engages the tube and at least one of the first and second threaded fitting members to establish a second seal against leakage of fluid pressure at temperatures which may relax the second fitting member and break the first seal. In a preferred embodiment the sealing member is made of silicone to maintain the second seal at the relatively high-temperatures.