On my way home from work, 2 days ago, my car started making a hissing noise coming from the front. The noise came and went and seemed worst around 50-70 mph. It seemed to be driving fine it just had this noise. I'm not really sure how to describe it, maybe like if you took preasure off of a hose? The noise stopped once I got off the highway.
The next morning...nothing. I didn't hear it at all. Then after work the noise was back. I wonder if it has something to do with how hot it gets during the day. It sits out in the sun and the last 2 days have been 90 degrees and above.
Does anyone have any idea what could be causing this noise?

 

Reaching on this, does this noise have anything to do with the cooling fans coming on and off?????

Then be sure to check the coolant level.

out on a limb on both of these......

 

AC refrigerant moving through the evaporator? Again, I'm kinda guessing.