Internal combustion engine with a liquid cooled cylinder head and a liquid-cooled cylinder block and method for operating such an internal combustion engine

Disclosed is an internal combustion engine (1) in the - the min. a cylinder head (1a) with min. has an integrated coolant jacket, said inlet side a first feed opening (2a) and on the outlet a first discharge opening (3a), - the cylinder block (1b) with min. has an integrated coolant jacket, said inlet side, a second feed opening (2b) and on the outlet a second discharge opening (3b), and - the first discharge opening (3a) via a first return line (5a), in which a heat exchanger (6) is arranged, and the second discharge opening (3b) with a control unit (7) are connected branches off from a supply line (8), in which a pump (9) to the feed openings (2a, 2b) and arranged to supply the coolant jackets, wherein a bypass line (5c) is provided, which from the first return line (5a) upstream of the heat exchanger (6) branches off to the control unit (7) leads, in which - the control unit (7) comprises a twistable about its longitudinal axis between the working positions of the control roller that the first return line in a first working position (5a) separated from the supply line (8) and the second return line (5b) and the bypass line (5c) to the feed line (8) connecting and separating the bypass line (5c) of the feed line (8) in a second operating position, and the two return lines (5a, 5b) connected to the supply line (8), and - the drive of the control unit (7) comprises a stepping motor, the control roller during the transfer from one working position to another Work pos. by a predeterminable angle Δα according min. rotated one step a predeterminable increment.