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Bled brakes maybe a tad too much

bp_vx

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Hey all

I was bleeding brakes this morning, done heaps of times before but got distracted and pumped until the ominous gurgle in the fluid reservoir. Stopped immediately and perhaps foolishly topped it up and finished bleeding the last brake.

Is the best thing to do now to bleed the whole system again? Will those air bubbles cause any problems making their way through the master cylinder or the brake booster? It would be the tiniest amount, didn’t run the whole reservoir dry, just low enough on one side that I think some air got in on the last pump.
 

_R_J_K_

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Yes, ideally you will need to do the entire thing again.
 

mpower

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bleeding them is to get the air bubbles out, you let air in.

do it again!
 

VT2Commie

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Stock up on fluid, ^^^like above the entire system will need to be done and quite possibly an ABS bleed with a scan tool that can command the ABS module, ideally.

See how a full system bleed goes, but if the brake pedal is still spongy after that, you may have air trapped in the ABS system also.
 

stick3

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i would do it again you may have to bench bleed the m/c and take it somewhere to get the abs checked using a tech 2 nothing worse when hit the brakes and the pedal its the floor

i brought a air bleeder of of ebay year and half ago and it came with a bottle you fill and invert into the m/c it come with different screw on legs to fit various m/c and saves it from emptying 20 odd bucks and i did both cars, cheap tool that make this job so easy now
https://www.ebay.com.au/itm/1L-Air-...512467&hash=item1eaaf895f6:g:dLYAAOSw99Rd-dMI
 

mechanic

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ou may have air trapped in the ABS system also
Unlikely unless the ABS has activated since air was introduced into the line. The ABS fluid/valve block is sealed. The even come pre-filled from the factory.
 

bp_vx

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Unlikely unless the ABS has activated since air was introduced into the line. The ABS fluid/valve block is sealed. The even come pre-filled from the factory.

So the fluid won’t pass through ABS on the way from the master cylinder to the calipers? If so then is there anywhere else air can get stuck? (Eg brake booster?)

Should I be able to feel sponginess with the vehicle off? I don’t feel any at the moment but will rebleed anyway. The two calipers I replaced seals in were pretty crusty inside. Whole system could use another flush anyway.
 

greenacc

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Brake booster does not contain any fluid. It only uses engine vacuum to help apply pressure on the master cylinder. An extra bleed will help clean out the system. Start at the back again. If it was me if you have to buy more fluid is get a different colour fluid this time so you can see it come through.
 

mechanic

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So the fluid won’t pass through ABS on the way from the master cylinder to the calipers?
No. The normal hydraulic system should be considered independent of the ABS component. Fluid bypasses the ABS valves/pump/accumulator until a tyre skids.
Then the ABS system opens valves and pumps fluid into and out of the normal hydraulic circuit. If there is air present in a line, it can inadvertently be drawn into the ABS valve block/accumulator.

(Technically the steel brake lines screw into the ABS valve block and fluid travels 'through' the ABS unit, but it should only be considered a junction/joiner for the brake lines)
 

Skylarking

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... Technically the steel brake lines screw into the ABS valve block and fluid travels 'through' the ABS unit, but it should only be considered a junction/joiner for the brake lines
As brake fluid is hygroscopic, we all know it needs to be periodically flushed and replaced with clean dry brake fluid.

From what I understand workshops have the diagnostic tools to command the appropriate ABS solenoids to open (and pumps to operate?) to aid the flushing process. Problem is, how does one flush the fluid from within the normally isolated ABS reservoir at home? And what volume of brake fluid lives within the normally isolated ABS fluid reservoir?

I’d think even a small amount of contaminated fluid living within the ABS unit will get into the brake lines and cause performance issues when the ABS unit operates, this is a time when you need it most :eek:
 
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