Ford Focus 2.0 tdci titanium 2006 - Ford Focus rumbling steering - minioneman

Hi, I have got a 2006 focus 2.0 tdci. Just recenly I have noticed that when it gets hot there is a rumbling noise coming from the steering when you turn the wheel. You can also feel this through the steering wheel. When it is cold it is fine. no noise or rumbling feeling. Just wondering if anyone has any ideas??