Hissing sound Vacuum leak with A/C on
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2005 Dodge Magnum
Hissing sound Vacuum leak with A/C on
I just bought a very clean well maintained 2005 E320 CDI from the original owner and I am in CA so I actually had to use the A/C for the first time yesterday and while I was cruising down the freeway I noticed a hissing sound that seemed like it was coming from the dash behind the gauge cluster. The sound would come and go as I accelerated and decelerated. It is very annoying and quite loud. When I turn the A/C off is seems to go away. Anyone experience this and what was the fix?
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From: Charlotte NC area
2019 WS222 S450 4-Matic / 2007 W211 E350 4Matic (Sold) / 2008 X164 GL320 CDI
Sounds like low Freon.
The expansion valve will hiss as it cycles if the pressure is low.
Have a good AC shop vacuum and fill the system and see if that fixes the issue.
The expansion valve will hiss as it cycles if the pressure is low.
Have a good AC shop vacuum and fill the system and see if that fixes the issue.
Thread Starter
Junior Member
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2005 Dodge Magnum
Low freon
The a/c is still cold, wouldn't low freon cause the a/c to not be cold? Or is this coomon for Mercedes?
Out Of Control!!
Joined: Aug 2010
Posts: 12,516
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From: Charlotte NC area
2019 WS222 S450 4-Matic / 2007 W211 E350 4Matic (Sold) / 2008 X164 GL320 CDI
When the system is just a little low gas can form on the high pressure side (normally all liquid) of the expansion valve and make a hissing noise.
It will still be cooling since it is just some gas and mostly liquid.
It is a common problem on almost every car with AC.
Thread Starter
Junior Member
Joined: Oct 2014
Posts: 35
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2005 Dodge Magnum
Hissing sound
The hissing sound comes and goes as I accelerate and decelerate and is there even if the a/c is off and just the fan is on. As soon as I turn off the fan it goes away. It almost seems like a vacuum operated door or something is leaking. I have owned many cars thru the years and when they get low on Freon the usual issue is that it is just not very cold and the compressor cycles, I have never heard a hissing sound like this on any car I have ever owned but I have never owned a Mercedes before. I am taking the car to a good mechanic on Monday to have the rotors turned and I will have him check to see if the Freon is low.
Out Of Control!!
Joined: Aug 2010
Posts: 12,516
Likes: 628
From: Charlotte NC area
2019 WS222 S450 4-Matic / 2007 W211 E350 4Matic (Sold) / 2008 X164 GL320 CDI
If the noise is with AC off, then it is most probably is not the Freon. (Maybe I misunderstood your first post)
I have had this noise on VW, Honda, Chrysler and other cars specifically when there was slightly low Freon.
I have had this noise on VW, Honda, Chrysler and other cars specifically when there was slightly low Freon.
