If the bumper covers become torn, can they be repaired or will it have to be replaced?

Anything can be fixed, the question actually is, is it worth it. There are kits to repair this type of plastic and body shops have all the stuff; the real costs are in the labor and the materials costs. The paint and the flexible materials and addatives used, etc, are really expensive. It will really depend on how bad the damage is. I've been told that some body shops won't repair them period due to "comebacks" - cracks that appear sometime after the repair. Whether this is bad preparation, trying to do to serious damage with the materials, or that repair doesn't work, I don't know.

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86 560SL
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85 380SL
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http://juliepalooza.8m.com/sl/mercedes.htm

do you know where bumper paint for a mercedes can be bought? Since I have an 87 420sel, the lower plastic cladding and bumper are different from the body. i went to my local Benz dealer but they do not carry the lower body paint anymore =(

I would just take it to a good body shop and let them do whatever magic is required to make them match.