Brake Fluid change

[riggaz]

Originally Posted By: hypervish
Hey everyone, hope everyone is doing well and happy holidays!

I want to change out my brake fluid sometime next week after my road trip. I don't want to damage the master cylinder as I've heard that's easy to do when bleeding brakes.

Here is the procedure I plan on using, please let me know if it's safe for the master cylinder.

1. Open brake fluid cap.
2. Pump brakes.
3. Open bleeder valve.
4. Close valve.
5. Pump brakes again.
6. Open bleeder valve.
7. Close valve.
8. And, continue that till the fluid is clean and I've done all 4 calipers.
9. Finally, close the brake fluid cap. ( I will monitor brake fluid and add as needed throughout the whole procedure)


You probably mean the same thing but the standard way to do it is

open reservoir and brim it
open bleed nipple
depress pedal to the floor and hold
close bleed nipple
release pedal
and repeat

remember you have about a litre of dirty fluid in the reservoir to flush out before you start pumping fresh fluid to the brakes, as a general rule you start with the furthest bleed nipple from the master cylinder first.

 

[CharBaby]

1 more quick step is to remove(if possible) as much old brake fluid from the resivior and pour in fresh fluid prior to starting the bleed. Otherwise, you're good to go!

 

[kam327]

Originally Posted By: riggaz
Originally Posted By: hypervish
Hey everyone, hope everyone is doing well and happy holidays!

I want to change out my brake fluid sometime next week after my road trip. I don't want to damage the master cylinder as I've heard that's easy to do when bleeding brakes.

Here is the procedure I plan on using, please let me know if it's safe for the master cylinder.

1. Open brake fluid cap.
2. Pump brakes.
3. Open bleeder valve.
4. Close valve.
5. Pump brakes again.
6. Open bleeder valve.
7. Close valve.
8. And, continue that till the fluid is clean and I've done all 4 calipers.
9. Finally, close the brake fluid cap. ( I will monitor brake fluid and add as needed throughout the whole procedure)


You probably mean the same thing but the standard way to do it is

open reservoir and brim it
open bleed nipple
depress pedal to the floor and hold
close bleed nipple
release pedal
and repeatremember you have about a litre of dirty fluid in the reservoir to flush out before you start pumping fresh fluid to the brakes, as a general rule you start with the furthest bleed nipple from the master cylinder first.


Buried in my long post above was the question: why do you need to close the bleeder valve after every pedal pump as long as you can prevent air from travelling all the way back up the tube from the drain container? That is a lot of extra work when you have to, in my experience, pump the brake pedal numerous times at least for the initial flush of the reservoir and the furthest caliper. As long as you either 1) buy a check valve to prevent air from getting up into the tubing to the caliber or 2) make sure the end of the drain tube is always immersed in fluid in the drain container, air can't get in and there's no need to open and close the bleeder valve dozens of times.

 

[Vikas]

Originally Posted By: kam327
As long as you either 1) buy a check valve to prevent air from getting up into the tubing to the caliber or 2) make sure the end of the drain tube is always immersed in fluid in the drain container, air can't get in and there's no need to open and close the bleeder valve dozens of times.


This is only a theory:- I suspect it is the threads on the bleeder nipple valve which could suck the air back in.

 

[kam327]

Plausable, but anal IMHO.

 

[mechtech2]

Originally Posted By: heyu
Originally Posted By: RiceCake
Originally Posted By: heyu
I always had good luck just changing out the fluid in just the master cylinder alone ,all the fluid in the lines does purge back and forth back to the cylinder so draining the master cylinder and refilling 3 - 4 times is usually all clean after that AND as mentioned above,,a turkey baster works great


Not really. Your brake lines are very long, narrow, and have no cyclical flow. Changing the brake fluid in the master cylinder regularly does cause a tiny bit of fluid to cycle into the top of the lines, but even in a million stops I doubt it will never cycle more then %5 new fluid to even the halfway mark down the lines.


Well you stand corrected ,,Any car i have emptied the master cylinder AND wiped clean with a paper towel had dirty fluid from the lines purged back to the master cylinder in less than a hundred miles (not a million stops that you claim) Have you never tried what i suggested for proof?? ,,Then what do you know to quote ? ,,I have even gravity bled rear brake lines through the master cylinder


Yes.
Whereas the fluid motion is not really CYCLICAL by definition, the fluid certainly does migrate and move around. Cyclical is simply an artificial wrong term. Turkey baster flushes of the brake reservoir are helpful indeed. It does help, and in some cases will fix problems as well as prevent them.

 

[heyu]

Originally Posted By: mechtech2
Originally Posted By: heyu
Originally Posted By: RiceCake
Originally Posted By: heyu
I always had good luck just changing out the fluid in just the master cylinder alone ,all the fluid in the lines does purge back and forth back to the cylinder so draining the master cylinder and refilling 3 - 4 times is usually all clean after that AND as mentioned above,,a turkey baster works great


Not really. Your brake lines are very long, narrow, and have no cyclical flow. Changing the brake fluid in the master cylinder regularly does cause a tiny bit of fluid to cycle into the top of the lines, but even in a million stops I doubt it will never cycle more then %5 new fluid to even the halfway mark down the lines.


Well you stand corrected ,,Any car i have emptied the master cylinder AND wiped clean with a paper towel had dirty fluid from the lines purged back to the master cylinder in less than a hundred miles (not a million stops that you claim) Have you never tried what i suggested for proof?? ,,Then what do you know to quote ? ,,I have even gravity bled rear brake lines through the master cylinder


Yes.
Whereas the fluid motion is not really CYCLICAL by definition, the fluid certainly does migrate and move around. Cyclical is simply an artificial wrong term. Turkey baster flushes of the brake reservoir are helpful indeed. It does help, and in some cases will fix problems as well as prevent them.


Well said and Very correct

 

[Tones]

Gravity bleed works well if your just doing a fluid swap. No pumping of the pedal so no danger of damaging anything.