IDIOMS

hot air

(idiomatic) Empty, confused, or exaggerated talk lacking meaning or substance; bluster.

Example:   The balloon was equipped with a burner to create hot air for lift.
1913, William MacLeod Raine, The Vision Splendid, ch. 8:
  "You'll never get anywhere so long as youse trail with that reform bunch. It's all hot air and tomfool theory."
1921, Alice Hegan Rice, Quin, ch. 28:
  "You give me a lot of hot air about your conscience. Why don't you get a soap-box and preach on the street-corners?"
2001 June 24, Johanna McGeary, "How Bad Is China?," Time (retrieved 22 Sept 2013):
  Some of the steam in Washington rises from real issues, but a lot is the hot air of partisan politics.