# Master cylinder and brake booster

**URL:** <https://community.cartalk.com/t/master-cylinder-and-brake-booster/1440>\
**Category:** Maintenance/Repairs\
**Created:** [July 8, 2007, 6:14pm UTC](https://community.cartalk.com/t/master-cylinder-and-brake-booster/1440 "2007-07-08T18:14:06Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![PghGasMan](https://avatars.discourse-cdn.com/v4/letter/p/91b2a8/32.png) [@PghGasMan](https://community.cartalk.com/u/PghGasMan)\
**Post date:** [July 8, 2007, 6:14pm UTC](https://community.cartalk.com/t/master-cylinder-and-brake-booster/1440/1 "2007-07-08T18:14:06Z")

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Recently I had my master cylinder replaced, my mechanic said it was leaking into the brake booster. After replacing it, he said he vacuumed excess brake fluid out of booster. Can this damage my brake booster?

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**Author:** ![willey](https://avatars.discourse-cdn.com/v4/letter/w/a9adbd/32.png) [@willey](https://community.cartalk.com/u/willey)\
**Post date:** [July 8, 2007, 6:15pm UTC](https://community.cartalk.com/t/master-cylinder-and-brake-booster/1440/2 "2007-07-08T18:15:37Z")

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Yes. Be prepared to replace the booster as well.

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**Author:** ![system](https://global.discourse-cdn.com/cartalk/original/3X/1/d/1d47c66a543aa6c5a7873bb2320858f978ff52ed.png) [@system](https://community.cartalk.com/u/system)\
**Post date:** [July 8, 2007, 6:32pm UTC](https://community.cartalk.com/t/master-cylinder-and-brake-booster/1440/3 "2007-07-08T18:32:29Z")

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What Wiley said. Brake fluid eats rubber. This includes the rubber diaphram inside the brake booster.  
~Michael

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**Author:** ![system](https://global.discourse-cdn.com/cartalk/original/3X/1/d/1d47c66a543aa6c5a7873bb2320858f978ff52ed.png) [@system](https://community.cartalk.com/u/system)\
**Post date:** [July 8, 2007, 6:37pm UTC](https://community.cartalk.com/t/master-cylinder-and-brake-booster/1440/4 "2007-07-08T18:37:54Z")

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Also your mechanic should have informed you of this possibility before starting the job. It would have been cheaper and more responsible to do both items at the same time.  
~Michael (Dartman69)

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**Author:** ![keith](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/keith/32/5518_2.png) [@keith](https://community.cartalk.com/u/keith)\
**Post date:** [July 9, 2007, 1:30am UTC](https://community.cartalk.com/t/master-cylinder-and-brake-booster/1440/5 "2007-07-09T01:30:25Z")

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> Brake fluid eats rubber.

Well we are in a heap o’ trouble here aren’t we. The brake system is full of rubber seals and rubber hoses.

The booster is OK and does not need to be replaced, but your mechanic missed an opportunity to make an extra boat payment. He’s gonna get kicked out of the shady mechanics club if he isn’t careful.

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**Author:** ![system](https://global.discourse-cdn.com/cartalk/original/3X/1/d/1d47c66a543aa6c5a7873bb2320858f978ff52ed.png) [@system](https://community.cartalk.com/u/system)\
**Post date:** [July 9, 2007, 3:55am UTC](https://community.cartalk.com/t/master-cylinder-and-brake-booster/1440/6 "2007-07-09T03:55:23Z")

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You calling me a shade tree mechanic out to make a buck off of an unsuspecting customer Keith? Tell you what smart \*ss go soak some rubber in brake fluid and watch what happens to it.  
Sorry it says annoymous I can not log in.  
Just so there is no confussion.  
DARTMAN69  
~Michael