Depends on the model year, engine type (8 or 16 valve) and whether air con is fitted. I only have info on the 1994 to 2000 year cars (Haynes workshop manual).
Are you sure the belt is routed correctly, it's easy to get it wrong when it goes round so many pulleys.
Is it a new belt, if so are you sure it's the right length?
sigg
July 2009