Over filling brake fluid

[Mr2Mike]

Bill3232 said:

Conclusion, I should remove some of the fluid from the reservoir returning the level to the high level mark and therefore giving the fluid the room to expand on future tempeture expansion.

Correct. Always check fluid level after a pad change; if someone has topped it up since the previous pad change then it will need some fluid to be removed.

[LordWhippy]

You do have to wonder, if there's no problem with overfilling it... why is there a max line?

[E-bmw]

Because there needs to be an air space above the liquid or operating the brakes will draw a vacuum. Conversely if the fluid gets hot it also needs somewhere to go.

Edited by E-bmw on Friday 28th June 10:14

[OnTheEdge]

E-bmw said:

Because there needs to be an air space above the liquid or operating the brakes will draw a vacuum. Conversely if the fluid gets hot it also needs somewhere to go.

Edited by E-bmw on Friday 28th June 10:14

As someone previously stated, vacuum is prevented by a rubber diaphragm and a vented cap (or sometimes just a vented cap). With the minimal airspace above the fluid when filled to the maximum level, a non vented cap would stop the brakes working in pretty short order.