Hissing noise under dash when ac on?

[PewterLS]

There has been a hissing noise (almost sounds like a vacume leak). On our way to the house this evening, I turned on the ac and I noticed that the hissing noise never went away like it had done in the past ( in the past it would only hoss maybe 5 seconds the. It would go away) and also the ac is not working. I checked out the ac compressor but it does seem that everything is doing fine so the ac should be on.
What do you think the noise is? It does sound exactly like a vacume leak but when I pulled the radio and the glove box I looked for a vacume hose but it does look like everything is electronic.

 

[joegr]

There are no vacuum lines under the dash. All climate servos are electric.

I suspect that you are hearing a problem with the expansion valve.

BTW, how could you tell "that everything is doing fine" when you looked at the AC compressor? The rest of us have to connect gauges and look up pressures in a table to tell if it is okay.

 

[PewterLS]

What I meant by that was the compressor cycles on and off ad normal. By this, I knew that the system is not low on freon and not allowing it it turn on as a reason for the ac not working anymore.

I will run it to a shop sometime this week and have it checked out then. What do you think I would be looking at I'd it is the expansion valve? This isn't a huge deal is it?
Also is the expansion valve the same as an orphis tube? If so is it inside the car or under neath the hood?
Thanks for the information and the help

I just don't trust shops that much and I know that they will say that it needs a full system to make a sell when it doesn't

 

[joegr]

What I meant by that was the compressor cycles on and off ad normal. By this, I knew that the system is not low on freon and not allowing it it turn on as a reason for the ac not working anymore.

I will run it to a shop sometime this week and have it checked out then. What do you think I would be looking at I'd it is the expansion valve? This isn't a huge deal is it?
Also is the expansion valve the same as an orphis tube? If so is it inside the car or under neath the hood?
Thanks for the information and the help

I just don't trust shops that much and I know that they will say that it needs a full system to make a sell when it doesn't

An orifice tube is a fixed metering valve that controls the flow of liquid refrigerant into the evaporator where it removes heat as it turns back into a gas. They are not very efficient as they always allow the same amount in, regardless of the heat load of the evaporator. To somewhat compensate for this, cycling clutch AC systems are used with them.

The LS uses a thermostatic expansion valve instead. The hotter the evaporator, them more refrigerant let in. When it gets colder, less is let in. The AC compressor is also a variable displacement type, so it adjusts how much it pumps, instead of cycling on and off. In low load conditions, it will still cycle on and off some since it can't reduce its displacement all the way to zero.

It is a really major job to replace the expansion valve because the whole dash has to be removed.

I am assuming (and should have asked) that you have full normal air-flow and that it just isn't cooled air. I am also assuming that while the air isn't cooled, it is not heated either. Failure of the DCCV is common and it causes the air on one or both sides to come out very hot all the time that the blower is running.

 

[PewterLS]

Wow. That is very informative. Thanks for the time and the details. I really appreciate! it.

Yes, I have full air running out of the vents. I can turn it to heat and it does blow hot and if I turn it down to 60 is it blowing out cooler air than with the heat but it is nothing that has been cycled through a coil and have been cooled.

 

[oddball]

You'll need to hook up gauges at the least to see where your pressures are at. You could still be very low on R143a - just enough that the fail safe doesn't disable the compressor, but not enough to actually cool.
Also watch out for oil leaking out the compressor. That'll cause the compressor to die before enough R143a leaks out to cause it to shut off. Look for a yellow streak running from the bottom of the front of the compressor towards the rear.

 

[rollingsolo]

I had the same issue on mine. Too bad I ignored it and now the compressor stopped working. I think the refrigerant is too low and now the ac clutch wont engage. DCCV has been replaced and every fuse has been checked. Anyone know an answer to this??

 

[joegr]

I had the same issue on mine. Too bad I ignored it and now the compressor stopped working. I think the refrigerant is too low and now the ac clutch wont engage. DCCV has been replaced and every fuse has been checked. Anyone know an answer to this??

Step one is to check the low side pressure.

If that's bad, then find and fix leak. Replace compressor if trashed and flush entire system.

If the pressure is okay, check for power at the AC clutch connector.

Power present - replace clutch.

No power - ...

 

[mmm]

There has been a hissing noise (almost sounds like a vacume leak). On our way to the house this evening, I turned on the ac and I noticed that the hissing noise never went away like it had done in the past ( in the past it would only hoss maybe 5 seconds the. It would go away) and also the ac is not working. I checked out the ac compressor but it does seem that everything is doing fine so the ac should be on.
What do you think the noise is? It does sound exactly like a vacume leak but when I pulled the radio and the glove box I looked for a vacume hose but it does look like everything is electronic.

Do you happen to know what you ended up doing to fix this??

Mine has the same issue, but does not show any other symptoms of DCCV valve.

Thanks.

 

[HALFGIG]

It is more than possible that you are just low on refrigerant (not out) just low. Make sure that it is checked correctly before going any further. The compressor may be pumping vapor at first until the liquid reaches it. That could be your hissing sound. Mine was low and did the same thing.

 

[mmm]

It is more than possible that you are just low on refrigerant (not out) just low. Make sure that it is checked correctly before going any further. The compressor may be pumping vapor at first until the liquid reaches it. That could be your hissing sound. Mine was low and did the same thing.

Thanks for the info!!

I will try adding a can first before anything else.

 

[LS4me]

I hear a "gurgling" sound behind the dash of both my '06s. It sounds a little like a gear cycling. It does it with the car running or not; and not always. Ideas?????

 

[joegr]

Thanks for the info!!

I will try adding a can first before anything else.

Please measure high and low side pressure before just adding a can of R-134a.

 

[joegr]

I hear a "gurgling" sound behind the dash of both my '06s. It sounds a little like a gear cycling. It does it with the car running or not; and not always. Ideas?????

To me, gurgling and a gear moving or grinding are different sounds.

Gurgling would tend to indicate air in the heater core due to a leak in the cooling system somewhere. It wouldn't be heard more than a few seconds after the engine shut down.

A gear moving (not grinding) sound is entirely normal, both while the engine is running and for several minutes afterwards. I have read that it is the climate control moving some of the air doors for some reason. I have no proof for or against this.

 

[BlackLS06]

I hear a "gurgling" sound behind the dash of both my '06s. It sounds a little like a gear cycling. It does it with the car running or not; and not always. Ideas?????

I have this as well.

Sounds like its behind the center ac vents?

 

[LS4me]

I have this as well.

Sounds like its behind the center ac vents?

Yes it does.

To me, gurgling and a gear moving or grinding are different sounds.

Gurgling would tend to indicate air in the heater core due to a leak in the cooling system somewhere. It wouldn't be heard more than a few seconds after the engine shut down.

A gear moving (not grinding) sound is entirely normal, both while the engine is running and for several minutes afterwards. I have read that it is the climate control moving some of the air doors for some reason. I have no proof for or against this.

It is more of a gear sound. The pitch oscillates like the gear is an irregular shape; like an egg maybe.

 

[joegr]

...It is more of a gear sound. The pitch oscillates like the gear is an irregular shape; like an egg maybe.

Yes, both of mine do this.

 

[1LoudLS]

I do get the hissing sound kinda like a vacuum leak, but it also has kinda a metallic sound to it, similar to the sound of water flowing through copper pipes in your house with a lot of turbulence. far to easy to just shut the AC off since it rarely ever gets hot enough here to use the AC.

 

[joegr]

I do get the hissing sound kinda like a vacuum leak, but it also has kinda a metallic sound to it, similar to the sound of water flowing through copper pipes in your house with a lot of turbulence. far to easy to just shut the AC off since it rarely ever gets hot enough here to use the AC.

It rarely gets cool (and dry) enough here not to need the AC. A hissing sort of sound when you first turn it on that goes away soon afterward is a sign of low refrigerant level. Even without any real leaks, some R-134a will seep through the hoses over the years.

 

[mmm]

So after hearing this same hissing / suction noise (can hear when my AC is running) for about a month and a half my AC finally decided to go out and blow only heat.

After reading many threads suggesting that the LS has a somewhat unique AC system, I decided it was best to take it to the dealer.

Turns out my DCCV or Coolant Control Valve (as they called it) went out. Went ahead and had the dealer replace, which I am still not sure why, because I definitely could have done it myself, but after 530 bucks later, my AC now blows cold again, BUTT

still have the mysterious hissing / suction sound coming from behind the dash. It will slightly hiss at idle, but if i go at least 5mph, the hiss will get loud, then stop and then after a few seconds, start low hissing again, slowly creeping up to a loud hiss and then stop. It pretty much repeats this over and over and over.

Oh, and the air from my driver side is colder than my passenger side.

Was wondering if anyone has found a fix for this yet.

I am kinda glad I did have the dealer replace the DCCV now, because they are going to diagnose this hissing sound tomorrow and not charge me an additional diagnostic fee. Which should have been included anyways, because I would think that their initial diagnostic should have included a pressure check of the AC system, especially if the customer comes in for an AC issue. I think they only did a code check and code said DCCV.

Anyways, if anyone has any info on this problem, please let me know. I will update on what they come up with.

Thanks...

 

[LS4me]

Vacuum leak? Ford has/had a habit of routing vacuum lines against heater hoses through the firewall. The heated hose "burns" a hole through the hard, plastic vacuum line(s). I had this happen on a Sable we once owned.

 

[joegr]

Vacuum leak? Ford has/had a habit of routing vacuum lines against heater hoses through the firewall. The heated hose "burns" a hole through the hard, plastic vacuum line(s). I had this happen on a Sable we once owned.

I don't believe that any vacuum lines run into the interior of the LS. Why would they?

 

[joegr]

...
Anyways, if anyone has any info on this problem, please let me know. I will update on what they come up with.

Thanks...

I had some hissing at startup when my refrigerant was low. It went away will I added refrigerant till I got the right pressures.

I suppose that a fault with the expansion valve might cause this.

It could be a leak with the brake vacuum booster if it happens with the AC off.

The LS doesn't have any vacuum controlled or activated items under the dash, so vacuum leaks should be out (other then the booster). Unlike the other cars that I have had, the AC doors are all electric, not vacuum.

 

[LS4me]

I don't believe that any vacuum lines run into the interior of the LS. Why would they?

I had some hissing at startup when my refrigerant was low. It went away will I added refrigerant till I got the right pressures.

I suppose that a fault with the expansion valve might cause this.

It could be a leak with the brake vacuum booster if it happens with the AC off.

The LS doesn't have any vacuum controlled or activated items under the dash, so vacuum leaks should be out (other then the booster). Unlike the other cars that I have had, the AC doors are all electric, not vacuum.

Don't know. Why the lines on the Sable? Blend doors?

I'm sure glad we have someone here as knowledgeable as you!! THANKS!!!

 

[mmm]

UPDATE:

Just got the diagnosis from the dealer.

Leak at the high side schrader valve is what they are claiming.

They said they normally charge $339 for this fix alone, but are giving me a cut in price since I already dropped $530 and then had to take it back again. They are charging me an additional $130.

I am going to get it fixed in a couple of days when they get the part in.

Has anyone else had this type of leak and if so were you also getting a suction sound??
Does the price sound right??

Thanks