Bumpers made of plastic are repaired by welding with an air heater or a large soldering iron.
Since the operation of removing and installing the bumper is not difficult, it is best to remove the repaired bumper from the car so as not to accidentally damage other body parts.
Clean the surfaces to be welded with some mild solvent. Connect the welded parts of the bumper and fix them with a clamp on a rigid stand.
If the bumper is deformed, soften it with a hair dryer, avoiding melting.
Set the softened bumper on a stand and give it the desired shape. Cool the bumper for 10 minutes. Place a small diameter tip on the hair dryer nozzle to get a directed jet of hot air. Heat the bumper parts to be welded with a hair dryer, moving the hair dryer to evenly melt the welded surfaces.
Prepare a thin welding rod by cutting it out of a scrap bumper. With the rod at right angles to the crack, fuse beads of plastic on both sides of the crack.
Fuse the plastic of the rod into the crack. Cut the weld seam flush with a torch. Sand the seam with 150 grit sandpaper without water, then polish with water with 600 grit sandpaper. Apply a coat of special plastic paint to the bumper.