Question about 1999 Jeep Grand Cherokee

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Brake makes a hissing noice when depressed

Heard a hissing noise all of a sudden

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  • sharonsnews Jan 26, 2009

    What am I looking for under the hood regarding a vacumn leak?

  • stevev357 Feb 05, 2009

    i have a 1999 jgc and i also hear a air sound comming from the inside of the car sounds like its comming from the brake pedal area , i have not checked my brake pads them selves ,but will check them out first and see what is up ! I will post any findings!

  • stevev357 Feb 05, 2009

    1999 jgc air noise comming from brake pedal area when pedal is pressed sound stops once pedal is released air sound is constant any ideas?

  • Anonymous Mar 13, 2014

    Press clutch hear hissing nois


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It may be a few different things, most of them relating to the brake booster. It could be a vacuum hose is loose or ripped (a simple fix, just replace the hose) which would correlate to a hissing noise outside the car. If there is a hissing noise inside the car it could be a tear in the booster on the inside of the car (trace the brake pedal up, at an angle, and then into a rubber 'boot' or 'fitting'. This is called the firewall by some people. With the car running (but in park) feel the rubber boot and see if you feel any air releasing, or if the noise diminishes when you cover certain parts of the boot). A tear internally means you need to replace the brake booster itself in some cases. This is a bit trickier to pull off if you don't have the experience.

Here is a picture of a standard booster/master cylinder.

Another (DANGEROUS) option if the booster itself is leaking is to disconnect the hose from the brake master cylinder, and clamp it off/plug the hose. This is the equivalent of having manual breaks, and will require a lot of pressure to engage the brakes (normally you are compressed air assisted by the booster). The only reason to do this is if the tear is large enough that you are losing engine power because of it. This will allow you to get to the next exit, next gas station, or (in some cases) 3 states away.

Posted on Feb 09, 2009

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Can you pinpoint where its comming from? like outside of car?under hood?or under dash? does car act or run any differnt when you apply the breaks?like maybe wanting to stall out? or breaks don't work right or low peddel? could be breaks grinding, time for break job? vacume leak to break booster or booster its self. taking a guess its time for breaks. need more info. to determin what the problem is.

Posted on Jan 26, 2009

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Check under the hood to see if you have a vac leak

Posted on Jan 26, 2009

  • Troy Bennett Jan 26, 2009

    there should be a hose from the break booster to engine check it to see if you here air wile running are you may need brake shoes the break booster can make a sound like you here but the brakes would be hard to press ( i hope this will help you )


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