# Hissing sound in the cabin - brake related

**URL:** <https://forums.speedlife.net/t/hissing-sound-in-the-cabin-brake-related/102910>\
**Category:** SON240sx Automotive\
**Created:** [January 9, 2007, 2:29pm UTC](https://forums.speedlife.net/t/hissing-sound-in-the-cabin-brake-related/102910 "2007-01-09T14:29:15Z")\
**Posts on this page:** 1\
**Showing post:** 8

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**Author:** ![DarkForceJackal](https://avatars.discourse-cdn.com/v4/letter/d/b38774/32.png) [@DarkForceJackal](https://forums.speedlife.net/u/DarkForceJackal)\
**Post date:** [January 10, 2007, 10:08am UTC](https://forums.speedlife.net/t/hissing-sound-in-the-cabin-brake-related/102910/8 "2007-01-10T10:08:02Z")

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> [@2000 Yukon XL Mods](https://forums.speedlife.net/t/2000-yukon-xl-mods/10877/10):
>
> now before i buy a MC and/or booster, i did mroe reading on old posts and it seems when the booster fails, everyone that has had that problem has a sinking pedle. Mine is just really hard and has very very minimal travel.
> 
> Any ideas? maybe the booster and MC are good, but the lines just need to be bled?

Perhaps the master cylinder is seizing and causing this kind of pedal feel? Hard to say.

I’d triple-check the vacuum line for a leak/crack as well as cheap insurance that that isn’t your problem.

Good luck.

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