The subject is my 1995 Miata. but this question could apply to a lot of older cars with bumper covers. How is the sag removed or do you replace the cover?
The subject is my 1995 Miata. but this question could apply to a lot of older cars with bumper covers. How is the sag removed or do you replace the cover?
When I worked at a shop, our standard practice was to heat the deformed area like crazy with a heat gun, push it into the desired position, then hit it with compressed air for a few minutes to cool it down and fix it in place. Repeat until it's the correct shape again.
A heat gun will heat up a small area. A pot full of near boiling water will quickly heat a large area.
I have reshaped dented bumper covers with this water method. Being mindful of the paint, I typically remove the bumper cover and pour the water onto the inside, un- painted side, of the bumper cover.
Or, is this a more Miata specific problem? Trying to remember my 90 Miata, is the problem that the skyward facing top part of the rear bumper cover should be a little curved, but over the years, and over the excessive heat, the positive curvature of the bumper becomes a negative curvature of the bumper?
Many bumper covers have styrofoam inserts below the cover to maintain shape. Would packing some styrofoam inserts to that area return the positive curvature?
Depending on the vehicle, I've had some success bonding an aluminum bar or something similar to the inside of the bumper to give it some support. Sikaflex 221 has worked great as an adhesive for this, on older cars where the bumper covers seem to be made almost of some kind of floppy urethane rather than the more sturdy ABS stuff we use today.
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