Engine roaring that increases with acceleration

It sounds like the entire front end is going to blow off, it is so loud. It is loudest when initially accelerating from a stop. If I increase speed from level speed, it either does not make the noise, which sounds like a loud roaring, or it is not as loud. Previously, the only time my car made any kind of "odd" or louder noise would be the first time I turned it on after not driving it for awhile, but it would stop within a minute or so. Now it is constant, no matter how long I have been driving.

The manager at the dealership says it is the electronic fan clutch that is so loud. I do not understand why it was not loud before, as I am assuming putting a new electronic fan clutch in should make it sound like it did before I had it towed in for the radiator.

There was nothing wrong with the clutch, they just replaced it to see if it would help and it did not. My car was extremely quiet from purchasing it new in 2008 until I got it back from being towed and having the radiator fixed. I do not understand why or what could have happened to make it become so loud, all of a sudden! There has got to be something wrong. Anyone have any suggestions or have had this happen before and found a solution?

Hi redrosepinkheart, what ever became of this as a diagnosis? My mercury mountaineer just started doing this over the past few months on random occasions. After I had exhaust replaced although coming from engine so probably no connection. This vehicle has had so many issues I hesitate to walk in a garage without a rough idea. :(