Abstract: Disclosed is a motor and pump which operate completely submerged in the pump fluid which uses surrounding fluid to cool the heat generated within the motor. The motor is also built with the intention that it can run in non-submerged applications by placing a cooling jacket around the stator portion of the motor and passing a cooling fluid through the jacket to absorb the motor heat. The cooling system disclosed is such that it can be filled with a fluid circulated within the system but not in direct contact with the fluid being pumped within the pump. Preferably the cooling system includes a flow control tube for use in controlling the flow rate of the cooling liquid and an expansion tank for use in limiting the pressure of the cooling fluid in the cooling system.