strange droneing sound

hello all i have just had another rover 45 diesel



all seems ok with it, but i am getting a strange low pitch drowning sound



coming from the drivers side of the engine, you cannot here it wen its cold it only make this noise when the engine has been running for a bit,



seems to be coming from one of the belts, cam belt or utility belt or from the water pump or steering pump or may be from inside the engine, i cannot pin it down, i know its not normal as my other 45 dose not make this noise.



its sounds like a repetitive rer rer rer rer rer sound low pitch



any ideas

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