Thanks for your advice DG and no worries about the wrong info, it stil led me in the right direction

I have done lots of DIY on cars in the past but not much on this E300 and MB do things differently to the likes of Saab and MG.

I now have the belt off, it was well and truly done in, with missing chunks of rib . I did buy the replacement a while back but have never got round to changing it, if I have realised it is not a hard job I would have done it agens ago. I have checked the tensioner and it appears to be fine, but I will follow your advice and procure a replacement. I have loosened the alternator now so as long as the replacement arrives tomorrow then I am in business.

As far as replacing the brushes and regulator.... I think I may well keep this unit as a spare and get replacements for it in due course.

In the mean time..... thanks for your advice and take care.

Daz