[s-cars] Brakes-S6, soft and spongy.. LONG

[Brian Armstead]

Not an expert on this Jeff, but you may have gotten some air in the ABS
unit.

Brian

"Postupack, Jeff" wrote:
> 
> Awright!  I need help, have to break down and seek S List counsel.
> 
> Situation is 1995.5 S6 Brakes.
> 
> Problem= spongy brakes, the pedal vibrates (lightly) when depressed, the
> brakes are not firm.
> Can't leave the property..
> 
> Observations:
> 1-Brake pedal was firm before I started mucking around!
> Why did I fix it?  I'll never answer that question!~ frankly needed to
> replace rear pads only.
> 2- I did NOT de-pressurize the bomb at the start, so I do not know the
> start condition of the Bomb.
> I 'later' read depressurizing the Bomb is advised.
> 
> 3- Front brakes are OEM, in fact this entire S6 is Stock.
> 
> Changed the REAR pads only, used a caliper piston compressor to open the
> gap, and reinstall.
> I had to open the rear bleeder to move (open)  the pistons and drain
> some brake fluid.
> 
> Bleeding: Built a pressure bleeder (thanks to Huw Powell, Tom Mullane)
> and bled all 4 corners.
> 
> I searched the S car list archives, Audiworld, S-cars.org , www.20V.org,
> and to my surprise I did not see a definitive brake bleed procedure for
> the
> C4 chassis specifically. A few writeups mentioned techniques for ABS
> equipped Audi's , tried to follow those ideas closely.
> 
> Yes, I read the Bentley,[ I own the paper manual set] not much there
> frankly..
> 
>  but I gotta tell you, the bleeding procedures by Phil Payne and 20V.org
> are much more comprehensive.
> 
> More Observations
> 1- The 1995.5 S6 does NOT have a brake proportioning valve located on
> the Left side rear wheel area.
> (My 1993 S4 DOES have this valve in the rear)
> 
> 2- My 1995.5 S6 does not have a bleeder at the Master Cylinder. (How do
> I clear the air from the MC?)
> 
> Method:
> 
> A: applied Super Blue with my Pressure bleeder at 10 PSI, Andrew made
> sure no air bubbles entered the MC under pressure.
> 
> B: I bled the Right Rear, Left Rear, Right Front, Left Front calipers ,
> the clutch slave cylinder first, in that order.
> 
> C: I started the engine and pressed the brake pedal, observed the pedal
> 'vibrated' slightly and then gradually moved forward, never reaching the
> firm pedal I noticed when I  STARTED this whole process.
> 
> D: NOW I think to test the BOMB, shut off the engine and tested number
> of pedal depresses.
> Counted 2, before the pedal got rock hard!
> 
> E: I pressure bled the system once again, more Super blue flowed into
> the spend tank!
> 
> F: I started the engine and pressed the brake pedal, observed the pedal
> 'vibrated' slightly and then gradually moved forward, never reaching the
> firm pedal I noticed when I  STARTED this whole process.
> 
> Same results. WTF!
> 
> I realize it is tough to diagnose via email,
> Is that BOMB dead?  It COULD have been on the verge of failure given 10
> year life.
> Is it possible I STILL have air in the system?
> 
> Whattaya think?
> 
> Posto
> 
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