C3 Corvette Bumper Repair - Rubber Revamp

Note that our V-groove runs the full length of the crack, and the cut is well into the thickness of the urethane cover, but not all the way through.

To protect the paint beyond the bumper cap, we masked the nose with a heavy tape line to the seam where the cap meets the body. This will save blending the new paint we plan to spray on the cap into the adjacent fiberglass. Even taped, sanding will require extreme care near the edge to avoid cutting through the paint we want to save.

Since the paint on our cover was basically shot, we stripped the worst of it for a repaint. Careful sanding with an autobody D/A sander and some detailed hand sanding quickly had the old finish removed.

A cold-welding compound, basically a highly specialized filler/glue, is a convenient and effective method of repair in this application. SEM No. 68442 Bumper Repair compound is made for the job. The catalyzed product comes in a dispenser that meters equal portions of the two components.

The repair material is applied much like body filler, but the working time is relatively short. Apply the filler a little proud (sticking up higher than the original or surrounding surface) of the original surface, but avoid overworking-aim to lay it down it in a few quick swipes.

Once cured, the SEM Bumper Repair compound can be sanded to shape. We found the material conformed well, and there was no evidence of it peeling at the sanded edges, indicating an exceptional bond.

To fill minor imperfections, we turned to a two-component glazing putty from Evercoat. These resin-based fillers are smooth sanding and flexible enough in thin layers to be useful in this type of repair.

A quick swipe of the glazing filler was enough to bury the remaining imperfections and the low spots left after sanding the bumper-repair compound.

Sanding with No. 150-grit paper gave us a smooth and well-feathered repair. At this stage, the offensive cracks in our bumper cover are gone.

Next, we prepared for refinishing. After stripping the paint from the opposite side, the nose of our Vette was carefully masked. Note that some additional filler was applied to the right side of the cover. This was to reduce some of the most objectionable waviness, a characteristic of these urethane covers.

A primer coat is needed to achieve a surface smooth enough for final paint. We used Nason 2K urethane, which is a high-build and fast-curing primer surfacer.

The primer was done in two stages: shooting the cover with two good wet coats, and then, once cured, sanding with No. 220 dry. This was followed by a second application of primer, consisting again of two coats.