Exhaust Flexible Pipe is a flexible piece of pipe that allows the exhaust system some flexibility. Exhaust Flexible Pipe is an essential part of any front-wheel-drive vehicle and on most all-wheel-drive vehicles. On front-wheel cars, since the motor is mounted transversely when you accelerate the motor rocks, the flex pipe protects your exhaust system from breakage. Without that extra flex pipe, the rocking motion would crack the exhaust system causing a loud leak. It is sometimes very easy to notice an Exhaust Flexible Pipe that is starting to break down. During the beginning stages, you may just hear a slight exhaust leak during your vehicle's start-up, and it will go away for the most part due to it not having a major leak, but when it finally does let go you will know it! Most flex pipes will break from the inside accordion piece, and it will sound as though you have no exhaust whatsoever. Other forms of a flex pipe leaking can be caused by your car bottoming out, and tearing the outer protective mesh, and scraping a hole into the flex tube, or it could just be from deterioration.