Abstract: A hydraulic unit with open-loop and closed-loop control of brake pressure in a brake circuit of an electronically slip-controllable braking system of a motor vehicle includes a pump housing, a motor for driving a brake pressure generator, and an electronic control device for controlling the motor in line with demand. The motor and the control device are disposed on opposite sides of the pump housing, and a shaft bore extending all the way through is formed therebetween, in which shaft bore a motor shaft which can be rotationally driven is disposed. A sealing apparatus seals the shaft bore with respect to an interior of the electronic control device. A sealing apparatus which comprises an insertion seal is disposed on the pump housing in a seal socket and a mechanical preloading force is applied by a preloading apparatus. A method of assembling the hydraulic unit is also provided.