A permanent-magnet synchronous electric motor with isolated rotor for circulation pumps of heating and/or conditioning systems having: a motor casing; a stator in the motor casing and having associated coils; a housing tightly isolated from the stator for hosting a permanent-magnet rotor; a shaft integral with the rotor; and a bearing supporting the shaft in the housing. The bearing has a bush rotatively engaged by one end of the shaft, a sleeve inserted at one end of the housing and keyed onto the bush, and a cap having a first portion removably inserted into the sleeve and a second portion screwly engaged in a threaded seat of the casing. This design has the major advantage of combining in a unitary part, the sleeve, the supporting function of the bearing and the hydraulic tightness with respect to the electronic components mounted at the bottom of the casing.
