The grill is absolutely fine. But two things, there is no need to be cooking ribs overnight. And I wouldn't suggest using the lower grate, the main grate is perfect for ribs. Try this. Four hours at 250 then wrap in foil and cook for another hour. You can adjust from there 👍
If you’re concerned, get a hot fire going, about 600*, and let her rip. Hotter isn’t really necessary. If you’re up to it, let it burn a basket of coal completely. It’ll be clean enough after that. Sent from my iPad using Tapatalk