C5 X7 aux belt tensioner.

[myglaren]

Coincidentally, perhaps Neil has the solution:-

viewtopic.php?p=864950#p864950

I'm sure that I have some square bits here. A quick and dirty search brings them up from several sources including Farnell:-
https://uk.farnell.com/wiha/7013-z-3-0m ... dp/1566736

[wurlycorner]

Different engine, but for reference Peter; on the suggestion of alternator over-run pulley being the cause - I did a video of what the symptoms looked like on my X7 (different engine, but definitely the alternator pulley that was the cause).
In this post here viewtopic.php?p=837574#p837574

[Peter.N.]

Its a brand new tensioner Mick, and it certainly isn't weak. I think I will try changing the alternator first - its much easier!.

Peter

[Lenny]

This is a better video..



...includes how to check the alternator clutch pulley.

It'd be a bit overkill to change the full alternator of it's just the pulley that's worn out.
Gates (the belt manufacturer) say the pulley and aux belt should be changed together. Both are a pretty normal service item.

[wurlycorner]

Gates (the belt manufacturer) say the pulley and aux belt should be changed together. Both are a pretty normal service item.

If you can get them... NLA for the 3.0 HDi alternator when I looked - not to mention impossible to access while on the car! (But that's 3.0 HDi specific woes for us idiots that own them and not relevant to this thread...)