Is it common for the plastic heater core box on the firewall to disentegrate? on 1996 Cadillac DeVille

I started smelling burning plastic from the engine compartment then I discovered the plastic housing is disentegrating due to engine temperature exposure. Bit of plastic are contacting the exhaust manifold. Is there a solution?

Asked by for the 1996 Cadillac DeVille
2 answers
yeah,one of the downfalls of GM products,the crumbly plenum box.just have to get a new one.
AGREE WITH #1