I've got a 99 Venture van that is making a hissing sound coming from the rear of the van, drivers side. I removed the interior panels and the sound is definitly coming from the HVAC lines that come up through the floor. I'm pretty much convinced that the sound is from the Thermal Expansion Valve not closing all of the way. The dilemma is that the AC works fine, which is a must down here in Houston, Texas. Basically the hissing sound is rather annoying. My question is can I let this sound alone until something else fails on the HVAC or should I get the valve repaired asap. I'm a home mechanic and I have done my share of HVAC work and in my experience you don't want to break into the HVAC lines without a darn good reason.
Well...an expansion valve almost hisses by its very nature so you might well end up with the same sound after a very severe and unwelcome intrusion into the hvac refrigerant circuit.
I would rather live with the sound.
May be using duct seal - that kind of putty that never hardens - around the valve area would absorb the high frequency noise....
Rear HVAC Hissing Sound
