New kid on the block

Hi my name is Tony Noble I have just bought a 1996 Disco and i think its the dogs whats its It will keep my MGB company. Yes i am patriotic. Can anyone advise me about a whistling noise on the engine the person I bought it off said it was the belt tensioner, anything I can do without replacing it . Keep it clean please Thanks

it could be roger whittaker has taken up residence under yer bonnet or maybe a leaky manifold..dunno about the tensioner as i've never heard one whistle