An IC engine has coolant distribution and discharge manifolds adjacent each other on one side of the cylinder block (10). Coolant enters the distribution manifold at a point intermediate the ends of the line of cylinders and from there flows freely up into the cylinder head through cast openings (52). The majority of coolant flows across the cylinder head and down to coolant chambers (58) surrounding the cylinder liners (20) via respective pairs of orificed holes (70 and 72) which control the flow of coolant around the cylinders and are provided in a head gasket (44). Coolant is discharged from the coolant chambers (58) to the discharge manifold. In order to prevent creation of an air pocket at the top of the discharge side of the coolant chambers (58), a portion of the coolant entering the head is routed directly, via a small opening (76 and 80). to the coolant chambers (58). To ensure that this coolant flow is distributed around the top of each cylinder liner (20), a deflector ledge (84) is situated directly below this coolant opening (80).