Depending on the year and configuration of the attachment locations can vary.
Front bumper
-open the hood.
-under the hood, Unscrew the screws (spun down) that secure the upper part.
-Unscrew the screws that attach the lower part.
-Unscrew the two nuts from the engine compartment.
-wrenched the wheel to the side.
-wheel arches free lockers (front part).
-attach the fender liner to the side and Unscrew the screws (nuts) holding the corners of the bumper to the wings.
-with the assistant pulls the bumper forward (look for wires).
-release the connectors on the Parking sensors, fog lights, temperature sensor (if any).
Rear bumper
-open the trunk lid.
-in the trunk and remove the rear side trim.
-the side casings, in the inner part of the wings, Unscrew one screw on each side.
-the plating of the rear panel Unscrew the two nuts.
-perimeter Unscrew the screws (spun upwards) from the bottom (if any).
-wheel arches free the wheel arches (rear).
-move the wing flaps to the side and Unscrew one screw on each side (spun upwards) holding the corners of the bumper to the wings.
-with the assistant pulls the bumper backwards (look for wires).
-snap together the connectors of the equipment (if any).
How to remove front and rear bumper Mercedes SLK R171
How to remove front and rear bumper Mercedes SLK R172