As long as we're talking about cooling fan operation, I think the fan shroud is at least worth noting. For the most part, it might seem like a hunk of plastic that gets in the way when you're trying to work on the engine, but it does serve a particular function. That function is to channel the air through the radiator to maximize the cooling fans effects. Without it, the fan cannot properly pull air through the radiator. A vehicle that doesn’t have a fan shroud and should is likely to overheat in traffic in the same way it would if the fan was not working. So if your vehicle is supposed to have a fan shroud and doesn't, find one, replace it, and recheck for your overheat problem.