Recently my car has started to make a creaking noise when I turn the steering wheel. It only seems to do it when the car is at a complete stop (engine turned on), and at very low speeds (like pulling out of a driveway). I checked the power steering fluid level, and it looks fine. It only seemed to start when the weather got colder, but that may be a coincidence. Would this indicate a need to change the power steering fluid? Could it be something else? Thanks in advance.