This study examines the intonational tunes of syntactically unmarked polar questions in Guanzhong Mandarin (GuanM), particularly focusing on the exploration of the boundary tone in Chinese languages and the interaction between tone sandhi rules and intonation. We conducted a production study with eight subjects on disyllabic words. The results show that the question intonation in GuanM has a higher and raised register, compared to the statement intonation, given higher F0 mean and higher F0 maximum and minimum in questions. In addition, the longer duration of the last syllable of questions but not the first syllable correlates with the established definition of boundary tones, which typically occur on the last syllable of the intonational phrase. Finally, in the T2T2 question intonation, the F0 change rate in the second syllable was higher, while in T1T1, it was lower, compared to statement counterparts, highlighting the necessity and a characteristic of the high boundary tone (H%) in the question intonation of Chinese dialects that it moderates the extent of the falling tone and facilitates the rising tone rising.