ABS Bleed

[ybkopa]

I'm having issues with my brakes. The brake pedal has no pressure once the car is running. I have bled all brake lines and the master cylinder however this has not fixed it.

The brake booster hose is also fine, there was a few splits but it has been repaired and there aren't any vacuum leaks from that line. The only thing I've found from other people who faced the same issue was that an ABS bleed fixed the issue.

I've tried bleeding the ABS, however VCDS never prompts me to open the caliper screw. It keeps repeating the steps of pressing the brake pedal 10x times over and over with the caliper screw closed.

Any help would be great as it is the last issue I'm facing right now.

[h100vw]

I'm having issues with my brakes. The brake pedal has no pressure once the car is running. I have bled all brake lines and the master cylinder however this has not fixed it.

The brake booster hose is also fine, there was a few splits but it has been repaired and there aren't any vacuum leaks from that line. The only thing I've found from other people who faced the same issue was that an ABS bleed fixed the issue.

I've tried bleeding the ABS, however VCDS never prompts me to open the caliper screw. It keeps repeating the steps of pressing the brake pedal 10x times over and over with the caliper screw closed.

Any help would be great as it is the last issue I'm facing right now.

Have you bled the master cylinder screws.

Sounds like you are carrying out the output test for the abs, not a bleed procedure

[ybkopa]

Have you bled the master cylinder screws.

Sounds like you are carrying out the output test for the abs, not a bleed procedure

Yep, I have bled both screws on the MC.

Regarding the ABS bleed, I'm in the ABS module and going into Basic Settings -> Group 1.

[MIG]

VWs method is to use a power bleeder, which makes the job much easier but the tool can be expensive $100-$200, and if you only doing it once, it's probably not worth it.

Try this with VCDS, it's a two-person job btw.

Select 03 ABS-Brake
Click on "04-Basic settings".
Select "Group 001" and press "GO".
Press down the brake pedal hard.
The ABS pump should automatically activate.
Open the bleed screw furthest from the master first.
Then click on "next".
The ABS pump will activate again.
Pump the brakes till no air bubbles remain.
Close the bleed screw.
Do not click on "next"; otherwise, the process restart

[beale187]

Ian has a great video on this
Pt 3 Epic Big Brake Upgrade Audi TT Mk2 - Brake master cylinder upgrade & VCDS brake bleeding guide - YouTube

[MIG]

Ian has a great video on this
Pt 3 Epic Big Brake Upgrade Audi TT Mk2 - Brake master cylinder upgrade & VCDS brake bleeding guide - YouTube

Great video on the brake bleed procedure

[ybkopa]

VWs method is to use a power bleeder, which makes the job much easier but the tool can be expensive $100-$200, and if you only doing it once, it's probably not worth it.

Try this with VCDS, it's a two-person job btw.

Select 03 ABS-Brake
Click on "04-Basic settings".
Select "Group 001" and press "GO".
Press down the brake pedal hard.
The ABS pump should automatically activate.
Open the bleed screw furthest from the master first.
Then click on "next".
The ABS pump will activate again.
Pump the brakes till no air bubbles remain.
Close the bleed screw.
Do not click on "next"; otherwise, the process restart

I'm using a pressure bleeder, however that hasn't helped much.
I'm pressing on the brake pedal at full force and the ABS pump does not activate.

I've watched Ian's video multiple times and VCDS will never prompt me to open the bleed screws like his one does.

[ybkopa]

Not sure if this was a good idea or not but I've just gone through an output test for the ABS and I've bled the MC screws whilst it was running. I got quite a lot of air out, started the car again and I'm still having the same issue.

The RPMS are also increasing and decreasing when pressing the brake pedal. I've taken the brake booster line off and smoke tested it. There are no leaks. I've also blown through the check valve and it's working as intended...

From my research, people fixed this issue when they bled their ABS but it isn't working for me :/

[MIG]

I wonder if the master is not building pressure to trigger the bleed cycle, did this issue just happen out of the blue, or did you change parts first?

Check the messuring blocks and see what pressure the system is building when you press the brake pedal.

Sent from my SM-N960F using Tapatalk

[ybkopa]

I wonder if the master is not building pressure to trigger the bleed cycle, did this issue just happen out of the blue, or did you change parts first?

Check the messuring blocks and see what pressure the system is building when you press the brake pedal.

Sent from my SM-N960F using Tapatalk

I did remove all 4 calipers for them to get painted. I also upgraded the rear calipers. However, I did clamp the lines before removing them so there wasn't that much fluid loss.

I'll look into the measuring blocks tomorrow and see what I can find out.

Hopefully all I need is a new MC and I can start driving this car again..

[MIG]

Hopefully all I need is a new MC and I can start driving this car again..

I have heard the MC seal can be damaged if the pedal is pressed too far when the system has no pressure in it, due to rust or pitting on sections of the piston that is not normally travelled.

But I would say that is rare, confirm it is the MC before throwing parts at it.