2002 E320. The AC makes a hissing sound once in a while. I took it into the shop and they said it blows cold and everything is fine. I told them it might me freeon. They said there is nothing wrong and it blows cold. I think I might have a leak? Or could it really need freeon?

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2015 ML350 4Matic. Wifes DD
2015 GLK350 4Matic. My winter DD
2012 E350 4Matic. Road Trip car
2009 CLK350 Coupe Designo.Kleemann Tune For nice days/DD
2006 CL600. V12.Eurocharged Tune. Enough said
2005 CLK55 AMG Coupe.Kleemann Tune. For the sound and style
2004 CLK320 Cabriolet. 2005+ Interior swap. For the sunny Florida days & beach days