The experiences of building a computer consultant to diagnose sources of noise in engine cooling systems are described. The emphasis for this project was on identifying appropriate parameters and writing rules to codify the knowledge. We have concluded that building a computer consulant using a commercial system is practical. A number of limitations are noted. For a successful comprehensive system the required resources to properly extract all the relevant expertise and to properly calibrate confidence factors will be large. Further development of the noise consultant will have higher payoff as a design aid rather than a diagnostic tool.