I can hear a strange noise when the truck is idling. The noise comes from the passenger side, possibly under the glovebox. From the drivers seat, that is where it seems to come from. There is two "clicks" I will call them, and then a releasing of air/gas/liquid/vapor, I am not sure. The shhhhhh noise somewhat resembles a respirator in a hospital breathing for someone. It seems to affect my idle a bit, maybe by 100 or 200 rpms. It drives me crazy. AC is not on, heater is not on. I can hear it when I am driving too, the engine kind of drowns it out. I have noticed no performance issues. It is just making me angry and I can't sit in my truck idling, because that noise pisses me off. I usually fix noises like that by turning the radio up, but the wife likes to talk when she rides along.

Any ideas? I have the helm manual and I haven't cracked into that for this issue yet. Thought I would use my best resource first, you!

Check and make sure all connections to and from the turbo are tight. When you are building boost, maybe air is escaping.

Pull your glove box off and see what you can see, takes about 20 seconds.

I would be really surprised if the turbo had something to do with it just because this sound is at idle. There is 0 boost at idle. I just finished fixing a leak in my intake (thing would howl like a banshee above 3 psi but silent at idle). How often does it make these sounds? Once in a while, every few minutes?

I can hear a strange noise when the truck is idling. The noise comes from the passenger side, possibly under the glovebox. From the drivers seat, that is where it seems to come from. There is two "clicks" I will call them, and then a releasing of air/gas/liquid/vapor, I am not sure. The shhhhhh noise somewhat resembles a respirator in a hospital breathing for someone. It seems to affect my idle a bit, maybe by 100 or 200 rpms. It drives me crazy. AC is not on, heater is not on. I can hear it when I am driving too, the engine kind of drowns it out. I have noticed no performance issues. It is just making me angry and I can't sit in my truck idling, because that noise pisses me off. I usually fix noises like that by turning the radio up, but the wife likes to talk when she rides along.

Any ideas? I have the helm manual and I haven't cracked into that for this issue yet. Thought I would use my best resource first, you!
Let's see behind the glove box and makes a whoosh sound while at idle and driving but a/c heater not on? sounds odd enough. I think you should take the box out and drive around.

that sounds like one of the vacuum lines that opens and closes the air ducts fof heating/cooling is bad inside the cab. Or the actuator that works the duck flaps is bad. I would saw disconnect the vacuum line into the cab and listen to see if the noise is still there.

I don't think any thing on the 6.5 diesels 94+ is vacuum actuated except for engine components like the EGR, and turbo control. I don't even have a vac. pump and everything inside my truck works just the way it did before I removed the pump.

I would be really surprised if the turbo had something to do with it just because this sound is at idle. There is 0 boost at idle. I just finished fixing a leak in my intake (thing would howl like a banshee above 3 psi but silent at idle). How often does it make these sounds? Once in a while, every few minutes?
The click click sssshhhshshshshshshhh seems to cycle once ever 20 seconds or so. I will try to dig in to it this weekend. I didn't notice it this morning. It was a little cooler this morning too. Maybe she has to be warmed up? I will look into it further.

I was thinking along the line of what Chicago TDP was saying. As long as the sound is coming from inside the cab (as we think anyway), this could really be the only thing that would make these kind of swishing/clicking sounds. I bet you've tried this already, but have you moved the vent selector around(floor/panel/defrost/combination of these) with different amounts of heat in each position? See if there is a change in frequency or volume of these sounds. Other than that, i'm out of ideas.:confused:

I figured it out. Thanks for the replies. I was changing the oil today and after the change, I started the truck and let it idle. Well I noticed that the AC compressor kicked on at the same intervals as the noise inside the truck. I went in the truck to listen and found it to be true. Well, even though my ventilation/climate system was off, it was on the defrost position. When I selected someting other than the defrost position, the AC compressor stopped turning on. Is this supposed to be this way?

Yes, the defrost runs the A/C too.

My bro in law left his '94 idling in a parking lot with his defrost on for two hours while he had a little "meeting" or something. Blew his crank pullet when the compressor seized.

Well that is no good. Is it supposed to activate the AC compressor even with my blower control set to off? I would think that nothing would be running at that time.

Maybe that's a bad switch. Mine only cycles when the fan's on.

Running the A/C system durring defrost is normal and it was designed to do this because when the cooler in the cab is cold it absorbs moister out of the air inside speeding defrosting.

Maybe that's a bad switch. Mine only cycles when the fan's on.

Just another's input:
My AC compressor doesn't cycle on/off when the fan switch is in the off position either.

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This week I noticed my AC wasn't blowing cold again. Last year I had the same problem and it turned out to be a faulty low-pressure switch. Checked that first, but it seemed fine. Took it to my bro-in-law for a refill and found the bolt holding the lines to the back of the compressor had come loose. Strange. $45 later I was blowing cold again.
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