Vacuum leak - whistle
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Post Fiend
Joined: Jan 2003
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From: Iowa
Vacuum leak - whistle
There's a vacuum leak somewhere under the dash of my '92 Exploder. It makes this annoying whistling noise, when the engine intake manifold vacuum is up (as when idling or cruising down the road. All the heater / AC controls work, the AC works great (retrofitted with R134a a few years ago). The only indication I have is that when on the Max AC position (recirculate), if I floor it (the gas), it will go back to drawing in outside air. Let off the gas, the whistling comes back and so does the recirculating air. The noise seems to be coming from under the dash, but can be heard outside the vehicle with the hood up.
This is not a real show stopper, just annoying. I'd like to get this taken care of before certain relatives find out about it. They like Chevies, and I'd never hear the end of it. Any ideas?
This is not a real show stopper, just annoying. I'd like to get this taken care of before certain relatives find out about it. They like Chevies, and I'd never hear the end of it. Any ideas?
Last edited by rusty70f100; Jul 16, 2005 at 01:01 PM.
Posting Guru
Joined: May 2002
Posts: 1,574
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From: Phoenix
Ok so you have a vacuum leak. I think the only vac actuated part of the HVAC system is the door for inside/outside air recirculation. 2 things happen when you go WOT. 1) the AC compressor kicks off. So if you sustain WOT for any period of time (30 +sec) you'll likely notice an increase in air temp because you've lost AC system pressure. 2) at WOT, vacuum goes to zero everywhere. So to keep vacuum actuated components where they should be, actuated, there should be a vacuum canister which holds vacuum until the engine can return it. Based on your descriptions, I would venture to guess that you have sprung a leak between the vac canister (accumulator) and the in/out air door actuator.
Elder User
Joined: Jan 2004
Posts: 805
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From: Pauline, South Carolina
Can you determine if it's inside under the dash or outside? One way to try and narrow it down is to use a tube that you can hold to your ear and try to narrow down the direction. Some folks use a paper towel or wrapping paper tube, or you can also use a vacuum cleaner hose (which is handy becaurse it's flexible). Two areas in particular to look at under the dash are at the control (there's a small manifold in back where the switch is to move the door), and at the actuator for the door (actuator may have sprung a leak). If it's a cracked hose, it will be more difficult to narrow down.
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