How To: Factory urethane bumper repair

Thomas_W · May 6, 2017

Since some parts for another project didnt show up today, i decided to start the repair on the Terminator rear bumper i bought a few weeks ago.

First up was to sand all the paint off from around the cracks and the hole in the bumper. This was done on both sides of the bumper with 36 grit sandpaper.

Everything was then cleaned with acetone. Then the cracks were glued into alignment with CA. You can see the blobs of glue in the above photo.

The inner surface of the cracks then were routed out with a rotary file running the length of the cracks and centered on the crack. This provides extra glue surface to hole the pieces together. The hole and cracks were then covered over on the painted side with clear packing tape leaving a bubble for extra material for shaping.

The inner surface of the bumper then had a flexible plastic mesh cut and tack glued into place covering the entire area of the hole and cracks along with some extra area outside of it all.

Here you can see the routed channel over the crack:

Here is a photo of the epoxy adhesive i used:

I then hung the bumper from my garage door track. This was so the epoxy wouldnt sag as badly as if it was laying flat.

Then all the epoxy was put in place, smoothed over and then some clear plastic was placed all over it. This was smoothed over and also to help contol any sag that may happen.

Once this side cure, ill basically repeat it for the other side minus the mesh and using some different product for getting the final shape just right. I'll also be shaving the cobra lettering, so that'll be included in the next posts as wl.

Thomas_W · May 7, 2017

The area where the hole was didnt get enough glue in it, so when i sanded down the cobra indentations, i sanded the hole area as well. I also routed out the channel over the cracks.

Then the epoxy was placed in position. Here is a photo of it in the process of doing the cobra indentations:

Once the epoxy was in the indentation, it was spread out. Then a piece of wax paper was put over it. This shows the high and low spots and also provides a shinier surface to see those spots:

Hen the epoxy was smoothed over to provide as close as possible final shape:

This was then repeated for all of the areas needing epoxy:

My flexible body filler should arrive tomorrow. So once i get back from running errands and fixing (another) water leak. Ill see about getting sanded down and some primer on it.

ttocs · May 8, 2017

I had a good tear in my front bumper that I did a repair on. Came out great can't tell there was ever a problem. Are you using a filler with fiberglass in it?

Thomas_W · May 8, 2017

ttocs said:
I had a good tear in my front bumper that I did a repair on. Came out great can't tell there was ever a problem. Are you using a filler with fiberglass in it?

Nope, all of the products im using are epoxy based and designed for use on a flexible bumper. With how shallow the repairs/shaving are, reinforced fillers are not really necessary.

Thomas_W · May 8, 2017

Once the epoxy was done curing i pulled the wax paper off. Here are the results:

Once i get back home from running errands, ill start sanding that down to final shape. Then once the flexible filler arrives I can start the final shaping and start adding primer.

Thomas_W · May 8, 2017

I got all the epoxy sanded down after a few hours (you have to work slow so it doesnt begin to melt). Then i put a layer of SEM Bumper Bite flexible filler on. This was then sanded down with some 150 grit paper. Here's a photo of it during and after sanding:

I then shot a coat of primer on the repair areas. Theres a few small imperfections but otherwise it looks great. One more small layer of filler and the entire bumper will be ready for block sanding and primer. Then the entire car starts going under the knife for body filler: