Input impedance measurement is commonly used in the design of internal combustion engines to improve their performance. The water-cooled charge-air cooler used in supercharged engines imposes a strong longitudinal thermal gradient on the air contained in its narrow channels. To isolate the resonances caused by the thermal gradient, the input impedance of a semi-infinite narrow pipe with multiple longitudinal temperature profiles is studied experimentally using the Two-Measurement Three-Calibration method. Three known non-resonant loads are used to calibrate the test bench. The importance of using a semi-infinite pipe as a calibration load in narrow pipes is further demonstrated. In the case of this paper, the acoustic propagation is highly influenced by the presence of microphones. The calibration process helps to take into account this influence. Measurements show that the presence of a non-uniform longitudinal temperature profile in the air inside a pipe modifies its input impedance.