I've done a Google Groups to try to discover how to cure the squeaking fan belt on the 300Tdi. Every solution is suggested from honey to expensive renewals!
One suggestion was a new belt from Quinton Hazell. So last week I phoned them and spoke to someone in their technical department. He recommended taking the glaze off the tensioner pulley with a piece of emery paper. Simple, cheap, and not likely to sell more belts so it had the ring of fact.
I just tried it. The squeak has gone! Of course, it may be due to fragments of emery powder doing the same thing as the honey, silicone lubricant, water, WD40, etc. that all cause the squeak to go short term and only time will tell.
If anyone else out there has the dreaded squeak, maybe they could try this and post the results. BTW, this is best done with the engine stopped!
Derry