If it's freezing you are worried about,it is not a problem.It is a couple of ounces of water at the most.If it freezes it can't do any harm because the ice has room to expand.If it was full of water,it would have nowhere else to go except through the sides.If you just want it bone dry jack the rear of the car up until the engine is level.Then it will all run out the water inlet in the middle.