The popping sound is probably from the heat expanding the parts. Might have less to do with it being water.I had an old-timer tell me this years ago, but I've never tried it. Nothing has an affinity for rust like water. Nothing penetrates rust like water. He said they would pour boiling water on rusted bolts. He said it works great. Sometimes you can even hear a popping sound as the chemical bonds break apart from the boiling water penetrating into the threads. One day I want to try this.