I agree with the elbows or water pump too, the elbows are on the tensioner asembly in case you don't know.
I would suggest you to take a look at the radiator passenger side cover, mine started to leak right below the filling neck and the result was a low coolant light everytime I started the engine, it would go away after a few seconds. One final possibility is the sensor has some goop on it. It's not that common but I've seen it in the forum. Members only cleaned it or replaced it.
Oscar.