Abstract: To assess face heating and frictional loading in a pump mechanical seal, a thermal–structural model was coupled to a mapping from friction torque to motor current and active input power. An L9 design, independent finite element verification, and four operating conditions identified a candidate with a balance ratio of 0.72, a face width of 8 mm, a stationary-ring thickness of 12 mm, and a spring preload of 250 N. Under nominal conditions, the maximum face temperature decreased from 140.88 to 93.53 °C, coning decreased by 72.70%, and friction torque decreased from 2.260 to 1.329 N.m. The additional motor current and input power both decreased by 41.22%. A five-indicator relative health assessment showed an average gain of 25.85 points across the four conditions. Relative wear-life factors ranged from 1.045 to 1.242.