Vacuum Leak Under Dash
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Joined: Apr 2006
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Vacuum Leak Under Dash
Just started having a light hissing noise under the dash (driver side) that disappears when the brake is applied. This is a late production 2004 Expy. This hasn't affected any systems - brakes and HVAC still work fine. I have noticed that the idle seems a little variable. Anybody else run into this?
Thanks,
Paul
Thanks,
Paul
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Joined: Jul 2004
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Hissing
This is really a shot in the dark. Many yrs ago I had a Mercury Grand Marquis that had automatic emerg brake pedal release. I also have this on my 2000 Nav--when emerg brake is set and I put the truck into drive the emerg brake immediately releases. A nice feature. Back to the Grand Marquis. I started hearing a hissing sound. Turns out that on that car there was a vacuum operated mechanism that released the emerg brake pedal. It's possible that you have this system on your truck---does the emerg brake pedal release when you put in drive? If so you should be able to find the valve under the dash--unplug the vac hose and plug with a golf tee--if that stops the hissing then you have a leaky valve. On my old car I just left it disconnected and plugged as the valve cost more than it was worth to me.
Hope this helps you
Hope this helps you
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Thanks for the suggestion - unfortunately, my '04 Expy doesn't have that feature. One of the dealership techs looked at it and thought it might be a brake light switch that, apparently, is vacuum operated. Another possibility was that it might be associated with the cruise control switch that shuts down the cruise control when you hit the brakes. I'll update the thread after tracking it down - I only hope it's not the brake booster.
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