Hissing Noise Under Dash

Morning All,

Need some help/suggestions on as to possible problems. Here's the scenario. I own a '02 Suburban -- LT/4x4. Driving into work this morning I heard a hissing noise from outside the vehicle. Though I was another vehicle so I didn't pay any attention to it. About 1 min later, the same noise started inside the vehicle, coming from under the dash on the right side. It lasted for about 5-10 secs them stopped. All gauges remained in normal range -- no change in drive/operation of vehicile. No noticable leaks, etc. Any ideas what it could be?

Thanks

Any smells and does your air still work? That happend to me in a volvo I had and a tube for the Freon that was rubbing on the frame and all the Freon leaked out.

Or it may be a vacuum line for the servo controls for the defrost/ air cond. system. Do your vents still work or does air come out of the same place no matter what you do with the switches (go from defrost to heater or windshield to floor and see what happends).

Keep in mind there is always some sort of hissing when the A/C is running. However, if you never noticed this sort of noise before that is a sign of something. Does your A/C still work? Freon is the only substance that will leak out under pressure on your Burb and not leave a tell tale sign. In other words, Freon is a gas and it won't leave any puddle as where all other systems utilize fluids and will leave evidence of a leak.
But there are still lots of vacuum secondaries and other air lines that could also emit a hiss as the air escapes out of them. Has anything stopped working on your Burb? Have you notice any sharp change in idle, acceleration or other sort of performance? Does your cruise control still work? These are all things that require manifold pressure to operate. I will be interested to see what you ever discover was the culprit here.
:confused:

Morning All,

Thanks for all the feedback. To answer your questions, there hasn't been any change in performance (A/C, engine, trans, etc), or anything else. Everything still works fine. For clarification, the noise was more of a areosol can being discharged (only loud) than a true hissing souund.

Thanks again.

lexismom