It's something that probably should be checked when it's serviced, whether it is I don't know. With regards to how I found out, it was simply a case that I noticed that there was a whining noise coming from under the bonnet. I knew it wasn't the power steering or anything like that since it was constant from when I turned the ignition on, not just when turning the wheel. All the fluids were ok, so I took it into the dealer to check it out. They said it was the pulley tensioner that was worn and after it was changed, problem solved.