1995 Jimmy makes odd noise!

I have just purchased a used 1995 jimmy 4 wheel drive with 52,300 miles. It has the rushing water sound that I have read about a 95 blazer on this forum. I have only been driving it for a month and the only thing I have noticed before now is the rushing water sound and fluctuation temperature gauge. Also the heat turned to cool air on one occasion and the temperature gauge pegged to the top of the scale. The other day I was driving on the four lane and something new popped up making me wonder if the previous owner traded it because of hidden problems. A loud whinning sound began and gradually increased in volume. I would kind of compare it to the tire running over those little groves they carve into the pavement to alert you that you are drifting off the pavement towards the guardrail. But I was not anywhere near the right front tire being on that grooved path. I was looking around to see if something passing me was making the noise but no one even was close. I pulled over and the sound decreased with speed. I pulled back onto the highway and continued on. After exiting onto another 4 lane around 3 mile or so later the sound began again and I pulled over one more time and the sound decreased with braking. I pulled out again and went on to my destination and returned home without any more incidences. Does anyone have any ideas? Please advise.