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Citroen c3 problems

Hi. citroen c3 2006 petrol. Where the brake pedal pushes the brake plunger, there is now a constant hiss but the brakes work fine. Any ideas? Many thanks

Posted by Chazaiki on


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Christian Barbera

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  • 6 Answers

Are you positive that there is nothing wrong with your transmission ?

Posted on Nov 27, 2013


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Jeremy W.

  • 5332 Answers

SOURCE: when releasing the brake pedal

Sounds like you have a leaking brake booster. The booster is what supplies the power assist to the brake pedal and is located in between the firewall and the brake mater cylinder.

Eventually it will get bad enough to cause either the check engine light to come on for lean codes or cause the engine to start to idle poorly and possibly affect you ability to apply the brakes.

This is a relatively simple repair. You can remove the master cylinder from the booster. Leave the brake lines attached. Most of the time you can gently move the master cylinder out of the way and the lines will bend or flex with the movement. You only need to move the master cylinder just enough to squeeze the booster in and out. Then remove the vacuum line from the booster.

The booster is held to the firewall with four nuts that can be accessed under the drivers side of the dash. First remove the rod that attaches the booster to the brake pedal. Then remove the nuts that hold the booster to the firewall. Remove the old booster and install the new one.

I’m happy to assist further over the phone at

Posted on Nov 26, 2010


old fart58

  • 163 Answers

SOURCE: 2005 Ford Escape Hissing sound

The power brake booster has a bad valve. I can't suggest where to find a new valve for it, but you can buy a rebuilt replacement. They are usually not hard to put on.

Posted on Jul 02, 2009


  • 10 Answers

SOURCE: Air/Hissing Noise from Brake Pedal

air may have gotten into your brake lines. try bleeding your brakes. this will require two people

Posted on May 29, 2009



  • 85239 Answers

SOURCE: Air/Hissing Noise from Brake Pedal

this noise is caused by a defective power brake vacuum booster, (big round thing behind the master cylinder) the diaphragm is leaking vacuum.

Posted on May 06, 2009


Paul W

  • 404 Answers

SOURCE: 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.

Posted on Jan 22, 2009

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Power brakes use a connection to the car's vacuum lines in order to make braking easier. It sounds like the seal around the plunger is leaking when it's cold outside. The plunger is the part that goes from the brake pedal, through the firewall, into the brake booster (vacuum chamber). The noise you are hearing sounds like some air leaking into the vacuum chamber of the brake booster.

If it's only happening when it's cold out, I'd probably not worry about it too much, unless it becomes a constant issue, even when warmer out. One of the drawbacks of this problem means that in order to get the same stopping power you used to have, you may have to exhibit more force on the brake pedal than when it's not leaking.

If you are worried about it, a competent shop could probably replace this seal for you, where as other "big box" shops will most likely tell you that you need to replace the entire brake booster assembly.

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