Abstract: A spool-shaped metallic heat barrier is inserted between the motor housing and the pump housing of a motor-pump assembly which conveys fluids at elevated temperatures. The flanges of the heat barrier abut against and are connected to the respective housings by means of bolts, and are rigidly secured to each other by several annuli of discrete heat dissipating ribs which are adjacent to the peripheries of the flanges. That flange which is adjacent to the motor housing can be formed with a peripheral groove the radially outermost portion of which receives a ring-shaped closure so that the inner portion of the groove forms an annular channel for reception of a stagnant or circulating liquid coolant.