make a clean breast of smth.

   ничeгo нe cкpывaть, вcё вылoжить, чиcтocepдeчнo пpизнaтьcя вo вcём, oткpoвeннo вcё paccкaзaть

    'I might as well make a clean breast of this, Mr. Butler,' he said throwing himself on the old man's sympathies (Th. Dreiser)