Xantia Aux Drive Belt Tensioner

[RichG]

I recently changed the Aux Drive Belt on my 1998 Xantia 1.9TD Estate after this group determined that this was the cause of a rattle on startup from cold. It cured the problem.
The rattle has now returned! On checking the new belt I found that the eccentric tensioning pulley had moved making the belt loose. The centre bolt was still tight to the Haynes spec. I have re adjusted the pulley and tightened the bolt as far as I dare. Has anybody else had this problem?
The Haynes manual says that my car, a pre face lift, should have the pulley on a bracket so that its position can be adjusted by a threaded bolt. The eccentric cam, according to Haynes, is only fitted to the 2.1TD engine. If the problem persists can I replace the excentric pulley by the bracketed one as it seems a much more effective method.
Richard Green