Replacing the Disintegrated Urethane on My 1983 Cadillac Sedan de Ville with Plastic That Lasts – David Conwill @Hemmings


Plastics are a mixed bag for the classic auto enthusiast. On the one hand, they can be formed into complex shapes at low cost, they’re lightweight, and they’re pretty durable (at least when new). On the other hand, they don’t age well, especially when repeatedly heat cycled or bombarded with ultraviolet light. As newer cars age, keeping them around is going to involve repairing or replacing all that aged plastic. My 1983 Cadillac Sedan de Ville is a prime example.

If you haven’t been following the saga of the Big Brown Cadillac, the important things to know are that it was built at Detroit’s Clark Street assembly plant in late 1982 and purchased toward the end of the 1983 model year by my wife’s grandfather, Bob. Bob bought the car (a) because it was a good deal (nobody wanted a brown Cadillac, apparently) and (b) to celebrate the birth of my wife, his first grandchild. Bob kept the Cadillac in immaculate condition, drove it with great care, and put only around 20,000 miles on it before he died in 2014. We acquired the Cadillac this spring and have been daily driving it while attempting to treat it with Bob-level care.

Although it has yet to hit 30,000 miles, the Cadillac definitely shows its age. The panels are all straight, and there’s not a speck of rust anywhere, but the clearcoat has faded through and much of the paint on the hood and decklid has lost its sheen. Worse yet, most of the urethane plastic that GM used to insulate the bumpers from the bodywork has broken apart

The original urethane fillers were designed to flex on impact, but they eventually fall apart with age.

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