Failing brakes..Help!

[MarcusDubya77]

So, long story short.. I swapped over to new rotors and removed my calipers to spray another color. I initially used a Motive power bleeder to try to do a one person flush. It didn't seem to work so I had my wife assist me and tried it that way. No good. I can't build any pressure even when I pump them (car on or off). Pedal just goes to the floor.There are some things I noticed.. The rears are fine and never had any bubbles. Front passenger had some bubbling. The driver side drained the whole reservoir and continued to contain air. There is also a horrible hissing coming from the brake reservoir area whenever the brakes are pressed. Any ideas? I am thinking it could be the master cylinder itself...


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[musasabi]

I had this exact same thing happen to me a few months ago. You said you "drained the entire reservoir". I know what you meant, but I'm willing to bet you drew air into all four lines without realizing it. It's easier than you think.

The way me and my buddy would up solving it was just doing a classic bleed. Furthest from the reservoir first, etc. That was the only solution after we let the res run dry by mistake for a single pump of the pedal.

Good luck!

[Peter1.8t]

Draining the resivoir is never good hopefully no air inside the ABS module. How did you bleed the fronts? Inside nipple first, then outside? And both sides of the caliper continued to contain air?

[badbluers4]

I think he forgot the back side bleeders.

[Peter1.8t]

I think he forgot the back side bleeders.

That's what I was thinking as well.

[MarcusDubya77]

It is probably a combo of all. I gonna do an ABS bleed as well as re-bleed..


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[MarcusDubya77]

The sequence I have seen for VCDS to ABS bleed is not working.. I went into ABS, Basic Settings, tried 001 and 002, but keep getting error. All wheels are off the ground. Anybody know what I am doing wrong??


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[MarcusDubya77]

Re-bled and re-bled... No Bueno. Ordered a new Master Cylinder, since symptoms point to a failed one.


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[EUROSWAGR]

What sequence are you bleeding the brakes in? You should also be using the power bleeder and are hopefully not trying to push fluid through the lines by pumping the pedal.
Now that you have air in the system, I'm not sure where to start, but I don't think throwing parts at the car is the answer. Maybe waste your money on a flatbed to a competent shop.

[TypeRx]

Dont know if you needed a new MC, but you probably needed to uninstall and bench bleed your existing one at the bare minimum. You might want to try that before installing a new one.

[FWP!]

It's air in the ABS system. Have to run the test to cycle the ABS pump which pushes out the bubbles. Have to do the same even on R8 LMS race cars. If you ran the reservoir empty, that's your issue assuming you've bled both bleeders on both front calipers.

[Peter1.8t]

The sequence I have seen for VCDS to ABS bleed is not working.. I went into ABS, Basic Settings, tried 001 and 002, but keep getting error. All wheels are off the ground. Anybody know what I am doing wrong??


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I've never had luck with activating it in basic settings. I think the forced readiness method works better for getting the ABS system to cycle.

[65vetteC6]

I would have to agree with others, if you run the system dry and below the abs module you will need to rebleed the system as FWP stated. Ordering a new master cylinder is not going to solve your problem

[MarcusDubya77]

Any link to a how to? I searched, but haven't had any luck.


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[MarcusDubya77]

Ran the readiness test... No Bueno... I just keep hearing this hissing from the reservoir cap area... Still full pedal play...


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[komseh]

Make sure the O-ring on your reservoir cap is in good shape.

[NY07RS4]

If you hear hissing, there is a leak. A leak will prevent the system from operating as designed. If you're certain it's coming form the res cap, replace it. That's one more item you'll be able to check off the list that could be contributing to your issue. At this point, I'd recommend having it taken to a trusted indy or dealer for a proper brake bleed service.

[MarcusDubya77]

Swapped caps.. Still hissing.. I am gonna swap out the master tomorrow...


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[Flying Tomatoes]

I think he forgot the back side bleeders.

That's what I was thinking as well.

Never saw a specific answer to this. Ive made this mistake myself and it can be quite frustrating, haha.

[MarcusDubya77]

Yeah, I bled all of the bleeders the third go around... Jabari reminded me.. I had stared right at them and made sure to put each on the proper side...So now I am at a crux.. I really think O might have over pressured the reservoir the first time I bled it. That's the only thing that I can think of.. Disassembly of the brakes and reassembly was straight forward.. I did let each line drain up front... That's about it.. I did pump the brakes on each corner when I would pressure bleed.. Just confused.. Hope the master cylinder fixes it.. I did push the pedal all the way in, so I don't know if that maybe affected it..


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[MarcusDubya77]

Finally solved after new master cylinder, 6 bleeds, and about 8 cycles of abs output test


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[Peter1.8t]

Finally solved after new master cylinder, 6 bleeds, and about 8 cycles of abs output test


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Wow that's crazy. Never heard of a master failing on these cars.

[MarcusDubya77]

I guess it happens. I will assume fault since I had my wife pressing the brake to the floor when we gravity bled it.. I heard that could cause some seal issues..


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[ven0m]

Finally solved after new master cylinder, 6 bleeds, and about 8 cycles of abs output test


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I had my reservoir run dry during a pressure bleed a while back (unlucky circumstances as the power bleeder had a 2'' silicon hose attached to the screw cover that reached inside the reservoir and when the power bleeder ran dry, the reservoir still had fluid inside, but the silicon hose reached past the fluid and pushed air directly in the front left brake caliper - IT WAS THE LAST ONE I WAS BLEEDING *bangs head against wall repeatedly*)

After failed attempts of manually re-power bleeding, I took it to the Audi dealer. We tried again manually to no avail. Also the Audi dealer said there is no function and no need of forcing the ABS cycle with VCDS - it says the same in the Bentley manual, after every brake bleed it is only recommended to force the ABS on the road once or twice - hard brake test. The only requirement is more than 2bar (30psi) pressure. The OEM Audi bleeder tool works at about 4 bar - it got all the air out in one bleed cycle (with my precious RBF600 also :'( ).

That's a lesson for the future on how not to waste a 100€ of brake fluid...

[Fourpoint282]

Finally solved after new master cylinder, 6 bleeds, and about 8 cycles of abs output test


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Hey you got a write up / diy on changing master cylinder? What's involved...I might be looking at this work too


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