The Cooling System Design Assistant (CoolSys), developed by the Knowledge Based Systems Laboratory at Texas A&M University for Chrysler Motors Corporation, is an integrated set of tools for engineering design support in the automobile cooling systems domain. In its primary mode of operation, the system models the reasoning process of an engineer as he develops design specifications for engine box cooling systems. The reasoning model has been effectively implemented using a situation specification technique that operates in the context of a history of design experimentation. Coolsys incorporates an existing engineering analysis model used to predict the performance of a proposed. cooling system design. The incorporation of this program, called the Thermal and Airflow Model, poses problems of symbolic numeric computing that have been addressed in Coolsys.