Combustion engine having at least three cylinders

The engine (1) has three cylinders arranged in series in a crank case (12). Two coolant channels (7, 8) are arranged in parallel to a longitudinal axis of the engine for the cylinder head and/or the crankcase. The coolant channels are connected with coolant by bar holes (9). A cylinder head (3) is transversely and partially flow throughable by the coolant along the longitudinal axis. A passage area of one of the coolant channels in a coolant flow direction is smaller while a passage area of the other coolant channel in the coolant flow direction is larger.