I have 2000 Suburban LT 4x4, lately I've noticed a humming noise coming from the front of the engine somewhere in the fan or water pump. It gets louder if I rev the engine. Also I see a streak mark of coolant on the inside of the hood cover but its' dry though. I look at my Temp gage and it's normal.Not sure if anybody had this problem before. Help!!! The noise is driving e crazy.