One of you guys might have a quick answer for this one: So I'm idling in a Starbucks drive through for about 15 minutes, waiting to go to the window, and I start to see a bit of steam vapor wafting up from the front of my hood. Not a lot of steam...but noticeable. When I pop the hood, the steam (with that hot coolant smell) is coming from these little vents (see photo). I think my electric fan "should" have come on during this? But temp gauge is steady in the normal middle position (there's no degree scale on the C30 temp gauge unfortunately). I know the coolant is quite hot, and if you own this model, you know this car runs pretty hot anyway, (and I'm not sure why that is). But I simply turned on the AC to test the fan, and it comes right on. Of course shuts off when you shut off the AC like it's supposed to. No other symptoms than that. But I don't think I want to get stuck in a freeway traffic jam having experienced this little "visual warning". I'm thinking thermostat? Your thoughts?