i have a tapping sound from the lower part of the engine a ford mondeo?

I had a tapping/rattling sound coming from the lower part of the engine on my new shape 2.0 Mondeo. The sound would get louder the warmer the engine got and would get even louder when I would switch on the air-con or windscreen demisters.
The fault was finally diagnosed to the aux belt tensioner (put a large screw driver to it and put your ear to the other of it and you will clearly hear it). The new part was £90 from Ford and it is resonably easy to fit.
I hope this helps.

Jon Hutter
November 2005