The traditional radiator is a Down-Flow type which has the inlet tank at the top and outlet tank at the bottom.

Another common form of radiator in current use is the Cross-Flow type in which the inlet tank is on one side, the core beside it and the outlet tank at the other side.

A less common type is the Multiple-Pass radiator. In a two pass design, the coolant both enters and exits from one tank that is divided internally. The coolant flows from the inlet side of the primary tank, flows through about half of the tubes to the end tank, and then returns via the other tubes to the outlet side of the primary tank. In this U flow type of design the primary tank is both inlet and outlet tank and the end tank is simply a way of returning the flow.