Well, I took the wheels off to change the brake pads and look at the vacuum pump only to see some debris around the auxiliary drive belt.
Lo and behold the centre bolt on the auto tensioner has sheared off. So tomorrow it's out with the drill and easyouts and tonight I pray for some good luck tomorrow. I may even be able to screw the sheared off bit right through as the tensioner is attached to the A/C pump mounting bracket.
The vacuum pump is actually very nice and quiet!
Anyone else heard of this problem? So pleased it did not let go altogether.
Ooooo I do love my Citroen