I have an 05 Ford Focus 1.6 TDCi which has done 130K. I have recently noticed a noise whenever I put any pressure at all towards the left on my steering wheel. The noise continues until the pressure on the wheel is released. It's difficult to describe the noise but a low pitched hum would probably be close. I don't want to go to a dealer witghout having some idea of what the problem could be so could anyone point me in the right direction.