[Engine] Black fluff around alternator belt area

[SeeRed]

I look after a Mk 1 Berlingo (DW8 engine) for a friend. It has had a new alternator belt (which is noisy and not fitted by me) and I've noted on the forum that talc might fix that. However, I noticed recently quite a quantity of 'black fluff' adhering to the bodywork just by the alternator pulley. it looks like fluffy rubber dust but the belt itself looks OK. Any ideas? 52 plate 1.9D and about 90k miles.

[Tomcat3]

Do all the pulleys line up? is it the correct belt?

[SeeRed]

Seems like the pulleys are chewing up the ribs on the belt, the tensioner is unlike anything I have seen in all the books. When putting a 4mm rod through the hole to hold it against the spring there is only a 'lug' to rest the end of the rod against, not a hole for it to go into which would be more secure.

The belt the garage fitted 6 months ago is a Gates micro v 6pk1438 (which a lot of places list as correct) but GSF list 6pk1388 which is 50mm shorter.

I'm wondering if there are two size tensioners. It has PAS but no air-con and is DW8 1.9D. When the garage fitted the new tensioner it is obvious they made a bad job of using an open ended wrench or spanner on the tensioner nut because it is quite knarled on a couple of the flats and may have 'sprung back' a few times before they managed to get it right = but a 15 ring spanner fits OK. I'm busy making a special tool to get the required leverage on this nut!

If I need to remove the tensioner is the hidden mounting bolt an allen key or a TORX? It looks in my inspection mirror to be a TORX. I've maintained classic Saabs for 40 years and have never worked on a Citroen before - and given the lack of access to these bits and pieces I am not sure I ever want to see one again!!

Finally, does the alternator pulley itself have an overrun clutch in it?