Underbody Flushing
WARNING: This page is about a different car, the 2004 Suzuki Swift + and 2004 Chevrolet Aveo. However, it is still accessible from the selected car via links, so may be relevant.
First, loosen the sediment packed in closed areas of the vehicle. Then flush the underbody with plain water. Flush the underbody of the vehicle at least once a year after the winter months. Flushing the underbody will remove any corrosive materials used for ice and snow removal and dust control.