The Opel Astra J diattor may be damaged by small pebbles and debris from under the wheels of the road ahead. This is related to the grille of the radiator that has quite large cells. The problem is solved by installing a fine metal mesh in the space between the bumper and the radiator.
It is not necessary to remove the bumper for the installation of the mesh. You need to remove the public number and the plastic grille that closes the heat sink. It is enough to pull it on itself, starting with the top. It will be easily clout and will come out. The grid should be attached to the rear of the plastic slats, and then put the grille in place.