2 Metaphors for purring

But place an engine in the hull and add to those fine lines the purr of a motorthere is a sight which brings a smile to the lips and a light in the eyes.

The door closed as she tried to pick herself up, the smooth purring of the motor became a leonine roar while she was still on her knees, gears clashed, and the car leaped with a jerk that drove her headlong against the cushions of the seat.

2 Metaphors for  purring