Melted Smoke Stack Grille

If you operate with smoke, just don't use the grilles. Smoking diesels leave me cold.  I have a couple, but never use them with smoke.

you can buy that part in brass and with a file make it fit. It's a PSC part.

You can also simply run the smoke at the low setting, which is certainly going to be more prototypical for most diesels.  I admit it, I'm a sucker for smoke, but with a diesel I run them at a lower setting, just enough to have a visible exhaust.  Not nearly as much heat, hence less damage to the plastic.

To expand on prrhorseshoecurve's good PSC partt comment, you could also get some brass at the hobby shop and use this as a simple scratch building/soldering/shaping learning exercise.

Easy piece, basic design, can't hurt anything because you would build it as a separate piece.

I was thinking about replacing the grille with one made from metal. I'll have to check that out. Or, as gunrunnerjohn stated, run the smoke unit on a lower setting. These engines don't seem to generate much smoke at the lower settings so that's why I have them set to high. I'm also considering the no grille option as well.

They're diesels, so smoke really isn't that important. It is a cool feature, though, and I find that my lone Proto-Sound 2 locomotive (20-2758-1, Western Maryland GP40) smokes better than any Proto-Sound 3 engine that I've owned.

Thanks for the replies! 

Just be aware that not all that long ago, I had a smoking MTH diesel on my bench with the top of the shell (cab) melted around the smoke stacks, over the smoke unit.
I think I'd go with John's suggestion to turn down the smoke unit.