Brake fluid circulation

[hennus]

I was experiencing brake fade and spongy pedal after some heated driving manoeuvres ( pun intended).Discs and pads good, so decided to change fluid.

.... Resulting in a sheared off nipple. Hardly applied much torque either.. For f sake!

Instead of drilling out and replacing the nipple I just drained the reservoir of its nasty brown liquid and refilled with some ATE super blue I had lying around and a dash of dot4.


How long will it take for this to mix around? If at all...

I know it's probably a lazy approach but I didn't want to a) only bleed one side, resulting in compressible liquid on one side but not the other. Or b) replace anything because I want to upgrade to 266mm discs/calipers/carriers soon

[PartyJas]

The new fluid wont mix with the old so you haven't really achieved anything with just changing the fluid in the reservoir. You need to sort the broken nipple and bleed the system through properly with new fluid.

[Eeyore]

er... If you have Sheared the nipple and already put air in the system I would assume its going to be near impossible bleed it all properly. You need to get that nipple sorted and do it all over again. What tool were you using on the nipple?

[hennus]

The new fluid wont mix with the old so you haven't really achieved anything with just changing the fluid in the reservoir. You need to sort the broken nipple and bleed the system through properly with new fluid.

Then how did the fluid in the reservoir get so brown in the first place? There must be some sort of diffusion happening at some rate. Don't know this from experience just instinctively. Although I did once bleed the brakes on an old bmw with a shared brake and clutch reservoir, switched to blue fluid but crucially didn't bleed the clutch- then when I came to bleed clutch some 6 months later it he become blue! (Hence some fluid circulation of some description...)

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er... If you have Sheared the nipple and already put air in the system I would assume its going to be near impossible bleed it all properly. You need to get that nipple sorted and do it all over again. What tool were you using on the nipple?

Sheered it before it opened! Was using an 11mm spanner

[daddyfixit]

1. it goes dirty due to degradation, the more moisture it absorbs causes it to effectively look rusty !
2. action of cylinder being used will allow some fluid to exit/re-enter reservoir but only moving through transfer ports in the cylinder--not the whole system
3. if different grades of fluid, or even mixing synthetic they may not mix....better to replace wheel cylinder/caliper so that you can carry out a full change properly by doing all 4 corners.

[Niall]

Im assuming it was a rear nipple that sheared. If so, bleed it from the line. Its not ideal but will get a hell of a lot more fluid through rather than just refilling the MC.