A rotor for cooling pumps is provided. The rotor is of the type which includes a core to be assembled on a shaft connected with an engine and a body, fitted in the core, provided with a plurality of radial tabs in flexible material. The core and the body with the tabs are both of a material like rubber, but with different hardness. In particular the core is made of a mixture of neoprene, nitrile, PVC and aramidic fiber. The rotor combines the features of lightness and wearproof of the rotors with a nylon core, but it is as strong and resistant as rotors with a metallic core.