I have a 2001 Chevy Impala. When the air conditioner is turned on, it makes this awful loud squealing noise. It sometimes does it even without the air conditioner on. When I look under the hood, there is a yellowish substance on the left side of the car where the belt and water pump are located. My warning light is on constantly 'Low Loolant Level' It has not overheated, but it has went a little past the half way mark.