Question about 1996 Jeep Grand Cherokee

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Brakes no power assistance, the servo doesn't appear to work, but I can hear hissing when I press brake pedal. I have been told a new diaphram has been fitted.

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If you hear hiss the diaphram is bad or was incorrectly installed. buy a coplete remanufactured unit they are tested before shipping to stores.

Posted on May 06, 2010


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1 Answer

My brake pedal will not budge, and a hissing noise present when running

The stop lights won't go out until the pedal is depressed, as there is a switch which is activated by the pedal.

A hard brake pedal is probably caused by a defective servo. The hissing noise is probably an air leak in the servo.

Switch the engine on, open the bonnet (the hood..) and see if you can locate the hissing - that'll probably be in the brake servo area.

If you don't know what a brake servo looks like here is a generic image:


Jan 27, 2016 | 1989 GMC Sierra

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Car looses power when brakes are pressed. In my 91 Buick Regal.

I wonder if you have an air leak in the brake servo? Check the manifold vacuum as you operate the brakes. Look for bad hoses around brake servo.

May 19, 2014 | Cars & Trucks

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Hi renault scenic 2l auto 2002. another common problem.

hissing noise is a leaking diaphram inside power brake have to replace the power brake booster.

Sep 18, 2012 | Renault Megane Cars & Trucks

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Brake pedal has alot of back pressure and car moves in gear.Have to press real hard to stop.How to check abs pump if has one where or brake booster or master cylinder?Don't know how to trouble shoot or...

The air seeping is a dead giveaway. Your power brakes are now manual brakes, but stiffer. The diaphram in the brake booster has torn and the hissing noise is the engine vacuum escaping (you hear it louder when you depress the pedal right?). Replace the booster and you will be fine. The brake lights probably don't work because you can't push the pedal down far enought to release the switch. Please rate. Thanks.

Sep 03, 2011 | 1995 Mercury Cougar

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1999 Buick Century Custom _ Brake Problem My 99 Century has little to no assist and it makes an air hissing sound when depressing the brake pedal. I think that this means that I have a faulty brake...

nope you have to replace them.when brake booster diaphram leaks you cant plug them.i have bought one at salvage yard in good shape.until i got a new one.get your brake booster from inside salvage yard where they stock them inside out the weather.dont take any brake booster off old outside cars been in all kinds bad weather. there vacuum diaphram probably dried up will leak also.

Jun 11, 2011 | 1999 Buick Century

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Hissing noise by brake pedal

On the other side of the fire wall is your brake power booster. It's what your master cylinder is attached to. It is vacuum controlled and has a diaphram on the inside. It sounds like you have developed a leak in that diaphram and as you press the brake pedal that is probably what your hearing. Is your brake pedal starting to get "hard" as that is what will start to happen as the leak gets worse. I hope this helped and good luck

Feb 19, 2011 | 2000 Chevrolet Blazer

1 Answer

Brake servo making a hissing sound around the brake pedal but

The brake booster is shot, there is a rubber diaphram inside the booster and it must be ruptured and is leaking vacuum. You may want to go to;, to see if the salvage yards in area have a used one.

Mar 21, 2010 | 2006 Volkswagen Passat

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1990 honda accord hard brakepedal and I hear air leak inside car when i press on brakes

Your power brake booster has gone bad, wont hold vacum the seal has gone bad, thats why you hear air and brake pedal is hard, booster sit under hood on drivers side fire wall, master cylinder bolts up to it, replacement is the only fix, unit can not be repair.

Jan 05, 2010 | 1990 Honda Accord

1 Answer

My 1989 Plymouth Horizon when I am stopped and holding my foot on the brake pedal I get a low hissing sound from somewhere in the car. I have checked all brake lines ad they are fine as well as master...

That hissing sound you hear is the brake booster, that big black round shaped thing that the brake master cylinder is bolted to, the diaphram inside, probably has a hole in it. Have to replace whole thing, not just the diaphram.

Mar 16, 2009 | 1989 Plymouth Horizon America

1 Answer

Hissing sound from brake pedal of Renault Scenic 2001

From your description this appears to be a Brake servo issue.
The brakes are assisted by a vacuum created from the draw off the inlet manifold, it gives assistance too the brake pedal pressure by a large tank/cylinder mounted on the Bulkhead/firewall.
I feel that the sound you a hearing is air being draw into the Brake Servo from the foot pedal seal and the reason for fluctuation in the engine is the vacuum from the inlet manifold is being upset.
Attention I suspect should be addressed to the Brake servo/pedal seal or gaitor.
I hope this clarifies your thoughts?
Please remember to rate my effort.
Paul 'W'
Onyer~EDSon(:0) {#><U.K.

Jan 22, 2009 | 2000 Renault 181

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