Results are reported of an analytical study of the character and magnitude of post mechanical interface separation in elastically supported rotary face seals subjected to particular types of input excitation. The seal system is approximated by lump system parameters which permit simulation of its dynamic response. Input forcing functions assigned to the mating ring include harmonic axial shaft pulsation and wobble due to misalignment. The equations of motion governing the seal carrier are solved to determine the character (stable or unstable) and magnitude (relative displacement at seal interface) of post mechanical separation for combinations of system parameters (spring constants, damping ratios, preset, inertia, etc.) and operating conditions (speed, degree of misalignment, amplitude of end play, etc.). For combinations of parameters normally encountered no unstable behavior was observed. However, a reversal of the effects of system damping between pre and post separation behavior did occur.Presented at the 25th ASLE Annual Meeting in Chicago, May 4–8, 1970