In 1967, Mr. P. Beatenbough presented the Thirteenth L. Ray Buckendale Lecture. The subject of his presentation was Engine Cooling Systems for Motor Trucks. In the twenty three years that have elapsed since that paper was presented, many significant advances have occurred in the field of engine cooling.This paper will explore those developments as well as discuss the functional issues involved in heavy truck cooling system design. Fundamental engineering concepts will be presented as well as simple conceptual models. Broad directions are suggested.