# Hissing sound from brake pedal?



## KingOfDirk (Jun 10, 2008)

Greetings all,
Sorry if this has been covered; I've searched the forums but can't find an answer so here goes:
My wife's '07 Rabbit 2.5 (MkV) makes a hissing sound coming from the brake pedal. When the pedal is depressed, it stops. There seems to be no loss of brake function, and as soon as the pedal is released it starts again. Any ideas?
Thanks in advance,
KingOfDirk


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## Old Dude GTI (Dec 25, 2007)

Does it hiss without ever touching the pedal?


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## KingOfDirk (Jun 10, 2008)

*Re: (Old Dude GTI)*

Yup. In fact, it *always* hisses unless I'm touching the brake.


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## Old Dude GTI (Dec 25, 2007)

Any chance you have climate control and your hearing a vacuum hose hissing? Does it hiss under the hood near the brake booster? I'm pretty stumped.


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## quattrofun5 (Aug 17, 2006)

*Re: Hissing sound from brake pedal? (KingOfDirk)*

My first inclination would be to check for a slithering reptile under the dash...
I've never heard of this problem before but do you have any driveability issues? If it was a vacuum leak, you would expect stumbling or some other issue but since the noise goes away when you press the brake pedal, it's possible. Can you determine whether the hiss comes from inside the cabin or the engine bay?


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## Old Dude GTI (Dec 25, 2007)

Is it possible there's a small hole in the booster diaphram? Idea! Unhook the vacuum line to the brake booster and plug it so it doesn't make noise or make the engine idle rough. Then listen for the noise.


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## GTijoejoe (Oct 6, 2001)

*Re: (Old Dude GTI)*


_Quote, originally posted by *Old Dude GTI* »_Is it possible there's a small hole in the booster diaphram? Idea! Unhook the vacuum line to the brake booster and plug it so it doesn't make noise or make the engine idle rough. Then listen for the noise.

good idea!
I x2 the vac leak from your booster. A reason why it will go away when you depress the pedal is because the internal chambers are opening to the atmosphere. If you pull a vac on the booster, and depress the pedal it will go to zero (if you stroke slowly) until a certain stroke, than it will close the chamber again. 
On a side note, I just did ^^^ yesterday because I thought I had a vac leak on my booster.
Gluck


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## HilF (Jan 10, 2004)

*Re: (GTijoejoe)*

does cruise control work?


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## where_2 (Jul 21, 2003)

*Re: (white_r!ce)*


_Quote, originally posted by *white_r!ce* »_does cruise control work?

My thought exactly, Cruise Control on earlier cars used a vacuum system which had a valve attached to the pedal. When you depressed the pedal even slightly, the vacuum in the system was released and the cruise was disengaged. A leak in the pedal valve typically caused the system not to be able to engage properly to control the speed of the vehicle. 
However, I am not certain how "drive by wire" handles cruise control, and whether the vehice in question has Drive By Wire. I know the TDI's got DBW years ago. Cruise controls on vehicles with turbochargers and superchargers are different than normal as well, since you cannot rely on having engine vacuum, you need a vacuum pump to create the vacuum source.


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## Lopakaj (Jan 24, 2005)

My 07 Gti has the exact same problem with the brake pedal. I took the car to the dealer yesterday and they replaced the brake booster. Only problem now they can't get the car to rev up over 3k. Don't know why that would have anything to do with engine speed other them a vac. leak.?. Hope it's nothing to do with the REVO...


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## JPick83 (Mar 14, 2008)

*Re: Hissing sound from brake pedal? (KingOfDirk)*

Im experiencing this same problem with my 07 Passat 2.0T.
The hissing sound seems to come from the brake pedal itself and disappears when the brake is touched. Let go of the brake & the hiss continues.
Any clue?


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## dsilbert (Mar 5, 2006)

*Re: Hissing sound from brake pedal? (JPick83)*

I have an '08 Passat 2.0t 6-sp manual. There is a hissing sound (vacuum leak??) coming from the brake pedal. Noise stops when brakes are applied. Hissing returns when foot comes off brake pedal. Any suggestions from those who also have had this issue and what has been the cure?


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## sipes_2003_GTI (Mar 27, 2007)

*Re: Hissing sound from brake pedal? (dsilbert)*

SAME HERE WITH MY 03 GTI ...


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## lynchman (Jan 29, 2003)

I just noticed this today on my 2008 Rabbit. Guess it's dealer time...


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## iTech (Dec 29, 2008)

The brake booster is leaking. It should under no circumstances make a hissing noise.


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## jfolt (Nov 5, 2008)

*bump*

Anyone ever figure this out? I noticed it a few months after I replaced my rear brakes. Didn't touch the lines, only pads and rotors so I didn't bleed brakes. Brakes work fine but hear that damn hissing noise every time I let go of the brake pedal...


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## smccracken (May 22, 2011)

*Hissing from Brake Pedal on A2*

Hissing is always there until the brake pedal is pressed.
Same as many have described before.
Does anyone have the solution to this problem?
Cheers
Steven


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## sleeper247 (Oct 2, 2009)

its that break booster its going to have to get replaced. Brought my 07 rabbit in yesterday, its going to cost me....sigh. Well at least I get a break flush out of it.


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## Jscharff (Dec 14, 2014)

Anyone get a rough estimate on hours they quote for the booster? Or better yet a DIY?


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