打破沙锅问到底
dǎ​pò​shā​guō​wèn​dào​dǐ

insist on probing to the bottom

  1. 打破 dǎ​pò verb + particle
    to break
    To smash, shatter, or break a physical object into pieces.
  2. 沙锅 沙鍋 shā​guō
    clay pot
    earthenware pot or casserole made of baked clay, used for cooking or boiling herbal medicine
  3. 问 問 wèn verb
    to ask
    to ask; to inquire; to request an answer from someone
  4. 到底 dào​dǐ verb
    to the end
    to reach the end; until the finish; to the last