A8 Parts Forum  

Go Back   A8 Parts Forum > A8 D2 > D2 - Axles, Brakes, Suspension and Steering

D2 - Axles, Brakes, Suspension and Steering Brakes, Springs, shocks, steering racks, steering columns, suspension arms, wheel hubs etc.

Reply
 
Thread Tools Display Modes
  #21  
Old 30th March 2019, 05:23 PM
hunker7 hunker7 is offline
Senior Member
 
Join Date: Jun 2018
Posts: 229
Default

See picture. Wouldn't move past that point in the tube.
Attached Thumbnails
Click image for larger version

Name:	15539677871835482692510895436644.jpg
Views:	230
Size:	308.3 KB
ID:	20997   Click image for larger version

Name:	15539678633996105211117426531298.jpg
Views:	231
Size:	241.9 KB
ID:	20998  
Reply With Quote
  #22  
Old 30th March 2019, 06:29 PM
MikkiJayne MikkiJayne is offline
Senior Member
 
Join Date: Jan 2012
Posts: 5,017
Default

A thought - is the pedal definitely returning all the way to its mechanical limit? If the pedal is pressed even a tiny bit it will cut off the supply from the reservoir.

I'm just wondering if the brake light switch is adjusted too far down and preventing the pedal returning fully. That would explain why you can't pressure bleed it (and is the only thing I can think of that would behave like that) and it could be that it goes to the floor just because its full of air.

I would pop the driver's side lower dash off and back the switch right off to see where the brake pedal stops and see if that helps before changing the master cylinder.

Remember to re-adjust the switch properly afterwards though. They have two sets of contacts which have to change at the same time and the ecus get in a grump if they are wrong.
Reply With Quote
  #23  
Old 30th March 2019, 06:33 PM
hunker7 hunker7 is offline
Senior Member
 
Join Date: Jun 2018
Posts: 229
Default

So even if master is gone, pressure bleeder should still force fluid through?
Reply With Quote
  #24  
Old 30th March 2019, 06:42 PM
MikkiJayne MikkiJayne is offline
Senior Member
 
Join Date: Jan 2012
Posts: 5,017
Default

Well, with the failure mode I described, the seals have failed. 2 bar should blow fluid through it no problem, unless somehow the seal has disintegrated and got stuck in the hole, but that seems highly unlikely.

I had an issue bleeding the clutch on the manual swap which was like this. I'd got the pedal stop about 2mm out which was enough to stop the pressure bleeder doing anything. Once I adjusted it properly it bled fine. I'm wondering if you're seeing the same thing.
Reply With Quote
  #25  
Old 30th March 2019, 06:50 PM
hunker7 hunker7 is offline
Senior Member
 
Join Date: Jun 2018
Posts: 229
Default

Pulled brake light switch outwards to make sure there is no pressure on the pedal and it can fully return. 2 bar in the brake fluid container and nothing. Not even a drop.
Reply With Quote
  #26  
Old 30th March 2019, 07:02 PM
hunker7 hunker7 is offline
Senior Member
 
Join Date: Jun 2018
Posts: 229
Default

Brake fluid level goes up and down as I press it?

EDIT: pedal seems to be stiffer now as well? But like I said still nothing at the back caliper.

Last edited by hunker7; 30th March 2019 at 07:06 PM.
Reply With Quote
  #27  
Old 31st March 2019, 12:01 PM
hunker7 hunker7 is offline
Senior Member
 
Join Date: Jun 2018
Posts: 229
Default

Decided to give her to my mechanic to sort out. Don't have time to deal with it myself and need it back by Friday.
Reply With Quote
  #28  
Old 4th April 2019, 03:43 PM
hunker7 hunker7 is offline
Senior Member
 
Join Date: Jun 2018
Posts: 229
Default

Quote:
Originally Posted by MikkiJayne
That is the exact symptoms of when I had a master cylinder fail due to the scenario I described. One circuit (ie one half of the master cylinder) failed so I had no brakes on FR and RL (or vice versa) and then once the pedal had almost reached the end of its travel, it braked on the other two wheels.
New master cylinder has been fitted, and brakes working. Pedal is still quite spongy, is that D2 thing or should be firm? Autos are usually pretty harsh.
Reply With Quote
  #29  
Old 4th April 2019, 03:46 PM
MikkiJayne MikkiJayne is offline
Senior Member
 
Join Date: Jan 2012
Posts: 5,017
Default

Non-Brembo brakes should be fairly firm. D2s are very hard to bleed properly though. Was the ESP pump cycled as part of the bleeding process?
Reply With Quote
  #30  
Old 4th April 2019, 04:01 PM
hunker7 hunker7 is offline
Senior Member
 
Join Date: Jun 2018
Posts: 229
Default

Quote:
Originally Posted by MikkiJayne View Post
Non-Brembo brakes should be fairly firm. D2s are very hard to bleed properly though. Was the ESP pump cycled as part of the bleeding process?
No idea if I have to be honest. Grabbed the car and left

How is it done?
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT. The time now is 03:11 PM.


Powered by vBulletin® Version 3.8.0
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.