# Brake fluid maintenance

**URL:** <https://community.cartalk.com/t/brake-fluid-maintenance/76197>\
**Category:** Maintenance/Repairs\
**Created:** [December 17, 2012, 4:00pm UTC](https://community.cartalk.com/t/brake-fluid-maintenance/76197 "2012-12-17T16:00:06Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![bogeymanii](https://avatars.discourse-cdn.com/v4/letter/b/c4cdca/32.png) [@bogeymanii](https://community.cartalk.com/u/bogeymanii)\
**Post date:** [December 17, 2012, 4:00pm UTC](https://community.cartalk.com/t/brake-fluid-maintenance/76197/1 "2012-12-17T16:00:06Z")

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Does the fluid in the master cylinder reservoir circulate to the slave cylinders or does it serve only as a reserve if fluid is lost to the system?

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**Author:** ![UncleTurbo](https://avatars.discourse-cdn.com/v4/letter/u/e9a140/32.png) [@UncleTurbo](https://community.cartalk.com/u/UncleTurbo)\
**Post date:** [December 17, 2012, 5:11pm UTC](https://community.cartalk.com/t/brake-fluid-maintenance/76197/2 "2012-12-17T17:11:59Z")

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Both. Eventually all the fluid in the system mixes together. The main purpose is a reservoir, but mixing does occur. There is no barrier between the fluid in the lines and the fluid in the reservoir tank.

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**Author:** ![circuitsmith](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/circuitsmith/32/40376_2.png) [@circuitsmith](https://community.cartalk.com/u/circuitsmith)\
**Post date:** [December 19, 2012, 7:34am UTC](https://community.cartalk.com/t/brake-fluid-maintenance/76197/3 "2012-12-19T07:34:05Z")

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The fluid mingles by the process of diffusion, but particulate crud obeys gravity and tends to settle in the lowest parts of the system.