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I initially thought it was the CCU fan that I've heard can make a buzzing sound.
However, this sound is hear in the cabin, but also pretty noticeable when the bonnet is open. http://youtu.be/Wmw1DoJXSSc
My oil cooling fan (at front righthand side) used to make such buzzing sound. Had it checked by shop. Turned out to be fan's holding rack was rusty and loose. Replaced with a new rack and the buzzing sound never came back.
Kidding aside, I'm no help if it is up close to the dash, but if it is from either front corner, then the fan of the oil cooler or aircon hitting it's housing sounds reasonable. But then it would be intermittent as they came on or off.
Q for the board: If it is fuel pump, is there some relay he could remove or something, and turn on the key, to see if the noise is still there?
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