2003 Ford Expedition hissing noise

2003 FORD EXPEDITION
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DOCVAUGHN
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Brakes problem
2003 Ford Expedition Four Wheel Drive Automatic 126000 miles

There is a hissing sound coming from the firewall behind the brake pedal that stops when I depress the brake. Could this be a vaccum leak?
Jul 6, 2010 at 8:56 PM
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JACOBANDNICKOLAS
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Yes, it sounds like a vacuum leak. It sounds like the brake booster is leaking or there is a leak in the hose that runs from the engine intake to the booster. If you can not see or find a leak, take the car to a nationally recognized parts store and have them to a vacuum test on the brake booster to see if it maintains vacuum.

Let me know what you find or if you have other questions.

Joe
Jul 7, 2010 at 10:50 PM