As my car it at the dealsership for a few days I woult be able to post a photo for the time being (got a 300C CRD as a loaner, for a diesel it's not bad) but, if you look at the picture above from AndyG you will see the part I am on about. It is just behind the suspension strutt and in front of the Fuse box, on the right hand side. It looks smaller than the IC pump posted above and made of Plastic. It aalos appears to bave a "blue" bit at the bottom in the picture above. Maybe that wil help you identify what I mean.
Cheers,

Si