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

[Mark Pollan]

Hi Jeff:

Ok so the only place you opened the system prior to bleeding was at the rear
bleeder screw where you would have had to open anyway to bleed so...

Me thinks your issue may be due to the inherent mechanical setup of the rear
calipers.  They need to be screwed in due to some sort of ratcheting that
occurs during e-brake application.  I would suggest repeatedly pulling the
e-brake handle.  IIRC I had to do this to adjust the rear piston so that the
travel is not so great.  Once this is done you will probably have to add
some brake fluid and hopefully your pedal feel will be back to normal.

Regards,

Mark



-----Original Message-----
From: s-car-list-bounces at audifans.com
[mailto:s-car-list-bounces at audifans.com] On Behalf Of Postupack, Jeff
Sent: Friday, April 21, 2006 11:50 AM
To: s-car-list at audifans.com
Subject: [s-cars] Brakes-S6, soft and spongy.. LONG



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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