A pipe diagnostic system includes a sensor capsule, measurement circuitry and a controller. The sensor capsule is configured to be coupled to an exterior surface of a pipe and has at least one temperature sensitive element disposed therein. The measurement circuitry is coupled to the sensor capsule and is configured to measure an electrical characteristic of the at least one temperature sensitive element and provide an indication of the measurement. The controller is coupled to the measurement circuitry and is configured to obtain a transmitter reference measurement and employ a heat transfer calculation with the transmitter reference measurement and the indication to generate an estimated process fluid temperature. The controller is further configured to obtain an indication of process fluid temperature and provide a pipe diagnostic indication based on a comparison of the estimated process fluid temperature and the obtained indication of process fluid temperature.