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Discussion Starter · #3 ·
thanks. It is not a constant his. it is there for a couple seconds and then off for a second. It sounds link a pump pressing down and hisses. when you pull the pump up, it stops.
 

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It's probably normal, as an AC system relies on heat exchange through a refrigerant expanding and contracting. The sound was probably the lines in the system pressurizing or de-pressuring.

HTH!
 

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Discussion Starter · #5 ·
thanks. The sound sounds like someone on a respirator.

I went to the dealer and we went in another acadia and the sound was not there. They said they will look at it tomorrow. Just hope they do not screw something up.
 

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Discussion Starter · #6 ·
The dealer said it is a AC fan that is out of balance. Does not sound like it to me, but they ordered one and it should be in tomorrow. I guess I will found out.
 

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Hi, I think that your AC system is low on freon. Please tell the dealer that you need a freon recharge and after it is charged check the system for noise rightaway. If there is a small leak in the system the charge won't leak out rightaway and hence you would be able to make sure if this will fix your problem or not. I am sorry to hear about this probelm, but recharging and making sure that all leaks are removed should fix this.
 

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I took my 2007 SLT, 62k, in to the dealer for the same issue. Loud hissing in dash when AC on. The dealer first said he could not hear it....then he said it was normal. I asked if the Freon was full and he said yes. I have had the car for 5 years. It was not hissing when I bought it and it had been getting louder/more persistent over time.

Trusting myself I took it to an independent shop. They reported .96lbs of r134 in system (spec is 2.32lbs). He was extremely intelligent and thought it sounded like the expansion valve trying to regulate the pressures. He replaced the Expansion Valve. It has been several days now and system is running great.

I have read others report this problem was solved by a Evaporator. In further research it appears that a new Expansion Valve is included with the replacement Evaporators. Leading me to believe that many people are paying for a whole core when in fact a valve is all that needs replaced.

I hope my luck holds, but one thing for certain is I will not be returning to my local dealer any time soon!!!
 

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Jayhawk said:
I took my 2007 SLT, 62k, in to the dealer for the same issue. Loud hissing in dash when AC on. The dealer first said he could not hear it....then he said it was normal. I asked if the Freon was full and he said yes. I have had the car for 5 years. It was not hissing when I bought it and it had been getting louder/more persistent over time.

Trusting myself I took it to an independent shop. They reported .96lbs of r134 in system (spec is 2.32lbs). He was extremely intelligent and thought it sounded like the expansion valve trying to regulate the pressures. He replaced the Expansion Valve. It has been several days now and system is running great.

I have read others report this problem was solved by a Evaporator. In further research it appears that a new Expansion Valve is included with the replacement Evaporators. Leading me to believe that many people are paying for a whole core when in fact a valve is all that needs replaced.

I hope my luck holds, but one thing for certain is I will not be returning to my local dealer any time soon!!!
Friend - I hope that it was found. For us, it was the hissing AC that did in our 07 SLT2. Seven repairs, where variously they could not find anything other than low coolant and filled it up. one time blamed on a bad schrader valve after the previous repair. Twice they replaced the dash controls. Hissing is the sound it makes to increase the pressure in the system, and as it gets lower and lower, the hissing will get more frequent. It got to be we could never know if some hissing was normal or not - because for two years there was always at least a little.

The last repair was made with a Caddy dealership and they got the inside evaporator which required dash removal - and they said they found it had both their florescent leak detection as well as older signs of leak detector. They said that the GMC dealer obviously had never laid eyes on the evaporator otherwise they would have put the fix in sooner.

I think (hope) they fixed it the last repair, but it was more than my wife could take. 3 trips in a row where the AC gave out and she wanted rid of it. The car was approaching 58k miles, and was all paid for - we decided to trade while the AC was working and before the car hit 60k miles. I am sure the dealer (who had a GMC in his network) pulled up the repair records and it probably impacted trade value. Traded for 40% of what we had paid 5 years before.

We knew we were taking a chance with a Version 1.0 car, but fell in love with the Acadia (which ride and comfort were still awesome after 5 years) - we didn't do the same thing this time. We got a 2012 Altima, at the very end of that model design right as the 2013 redesign hit the lot. Save a ton of money.
 

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I am having a similar experience with mine now, but mine is while the heat Is running. Every 2 minutes or so I hear the hissing noise that almost seems like a pressure relief or something. Sounds like it is cycling more often then not. It will be quiet and then hiss for about 15 seconds or so then quiet until the next round. Does this sound about the same?
 

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Last post here is from 2012, but I'm experiencing this same thing on my newly acquired 2016 Acadia. I'm going to take it in and have them look at the evaporator valve and check freon, etc. I wish consumers didn't have to tell the dealers what to fix, and they could just fix it based off symptoms.

I'll post again once I get it looked at.
 

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Last Update from me.

It turns out the issue was a leaking evaporator core, and there was also low refrigerant. So there you go, 2016 Acadia has the same problem.

Enjoy.
Thank you for your update. I'm experiencing the same issue. Taking it to the shop this week. Atleast I can tell them what to look for.
 

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He hasn't posted for 7 months, but he might be watching... (plus always good for reference for others).
My guess is there's a mad snake in there. :eek:
 

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Makes me happy I bought an extended warranty on my Acadia. I am more than capable of replacing an evaporator as I have done a couple along with heater cores in the past. But to pretty much waste a whole day or in my case probably a weekend because of my job hours, let the dealer do it and get a loaner out of it.

Does anyone know why the front evaporator fails like it does? I have read about the rear evaporator and the blower motor cage particles contaminating it but I have read nothing on reasons for the front failures. I feel like at 10 years in to the model run that inferior parts would have been replaced by better quality stuff at this point. Wishful thinking on my part?
 

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I just recently started having this hissing sound on my 2016 acadia slt. My AC blows warm air and the hissing comes and goes for like 30 seconds..I have the extended warranty, so I'm taking it to the dealership on Monday. So glad I read this comments.
 

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I just recently started having this hissing sound on my 2016 acadia slt. My AC blows warm air and the hissing comes and goes for like 30 seconds..I have the extended warranty, so I'm taking it to the dealership on Monday. So glad I read this comments.
Please post again with the results of your trip to the dealer. It sounds like to me that it is not a question of if, but when, my Acadia will start doing this. I guess the bright side to this is that since both the front and rear evaporator cores are prone to failing prematurely, the total cost to fix both will easily exceed the cost of the extended bumper to bumper I bought. The negative side to this is that if GM hasn't spec'd better designed parts to prevent this expensive and unnecessary repair, then it is going to fail again and in my case, I will be stuck having to fix it. For the mechanically challenged, I would reasonably expect someone to be pissed off at the high repair cost.
 

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Does anyone know why the front evaporator fails like it does? ...
I firmly believe the weak link in this system is the thermal expansion valve (TXV). They (GM) sell the TXV as an integral part of the evaporator as well as a separate part on most parts listings. It's beyond comprehension why engineers didn't design a firewall access to this ~$10 part to make a change easier to do. Some resourceful tech could probably find a way to do that and provide their customers less costly A/C system repairs.
 

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I firmly believe the weak link in this system is the thermal expansion valve (TXV). They (GM) sell the TXV as an integral part of the evaporator as well as a separate part on most parts listings. It's beyond comprehension why engineers didn't design a firewall access to this ~$10 part to make a change easier to do. Some resourceful tech could probably find a way to do that and provide their customers less costly repairs.
Some of the things engineers have done over the years are beyond comprehension, and as a result, we the consumer end up paying the price. It is what it is. I'll deal with it if and when the problem comes up. I'll talk to my guy at my local dealership and see what he says.
 
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