I bought a Mondeo from a garage and have got a knocking noise underneath the car. They say it has had a new clutch cable fitted, which is on a floating sub frame and it is nothing to worry about. I am not sure about it and am thinking of taking it further with the garage that they got it MOT'd at, because I know they are a dodgy place. Personally I think that it could be the engine mounts or gearbox, but I don't know.