W124 with Darth Vader breathing sound

Hi Group
Just got a 92, W124. When driving there is a breathing sound from the engine room that comes regulary butt not in rytmic intervals. It sounds
like some kind of pump or valve that lets of pressure. Can anyone explain what this sound is?
Thx.
Christian Jonbech
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Kind of a 'ggsshhh' sound? It may be the 'freon' going through the air conditioning plumbing in the dashboard.
John M. "This is '94 E320"
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Mmm... it can be the expansion valve... it is a metering device... but only with A/C on... Never heard of this problem though.
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