The predictive maintenance of the machine performance in any Oil Company is based on the mechanical vibration, different in sounds and different in temperatures on the machine. The machine may crash and stop working at any moment if there is no maintenance schedule. Furthermore, The Mechanical loss or the bearing friction loss produces heat loss. Heat generated has a direct influence on bearings service life. This paper studies and investigates the temperature distributions and heat loss by bearings in the horizontal centrifugal pump located at the desalination unit of the first stage in Azzawiya Oil Refining Company, which is part of the predictive maintenance program subjected to the regular inspections vibrometricas in each year periodically The results illustrated that the temperatures ranged between 27.06 °C and 61.15 oC and the average temperatures were 55.15 oC........................ Keywords: ...............mechanical loss, Centrifugal, Temperature, bearing. Pump.