S4 Brake Help pls.

[docurley]

You did take the hand brake off?

[innov8]

Hi Docurley. Yes, I double checked that the brake was off. The rotors also turned easily and I double checked the master cylinder to be sure that the cap was off. I nearly bent the hand of the special tool that I am renting from Autozone!!! that thing is stuck! Any ideas? Thanks.

[docurley]

have you tried turning it both ways as it seems strange your brakes where working before!!!

[innov8]

Yes, Turning counter clockwise, pulls the tool away from the cylinder and turning it clockwise pushed the cylinder in but it would not budge. Becuase the pads in this stubborn side of the car (drivers side) were significantly more worn than the passenger side, wouldn't that indicate that they were not retracting when the brake pedal releases? If the cylinder in the driver side caliper was bound or seized, would it produce this uneven pad wear? I'm at a loss as to what to try next, expect for replacing the caliper or taking the car into my mechanic. What would you do?

[docurley]

Well I would soak them in WD40 and may be a little push on the pedal a little to see if the piston moves but make sure you have something in them so the dont push out fully and you can still get the tool in to wind them back.

I will have a hunt around and see if I can find some more info.

[innov8]

Cool. Thanks for the research...I am at a loss. Nothing in the manuals that I have and I can't seem to find anything else through the parts houses... no caliper rebuild kits or anything like that.

[innov8]

Hello again. The passanger side caliper seems seized or something... I am still not able to get the DS caliper piston (cylinder) to retract using the special tool. I have attached images below of how I removed the rotor and re-attached the caliper so that I could put more leverage onto the caliper without damaging the break lines. It still won't budge after putting ALL my weight (200lbs) on it. I then tried a helper stepping on the brakes (master cylinder capped) and the cylinder doesn't move...either it is seized or so extended (see picture below) that it is beyond retracting. My questions: 1)...does anyone have a solution, short of replacing the caliper? and 2) is there a tech article on replacing a caliper that I can follow?

The above tech was very, very useful and I am now confident that I could replace the caliper with your help.

S4:DScaliper2.jpg
This is the caliper with the special tool attached (rotor removed)

S4:DScaliper:cylinder2.jpg
Close up of cylinder in question... over extended or seized?

S4:DScaliper3.jpg
Another view of same problem

S4:PSfinished.jpg
Here is the passenger side...finished. Thanks for your help!
Patrick

[docurley]

The tool you got does it have the two niples that lock in to the caliper as these will turn the piston round winding it back, if it's just pushing back without winding the piston it will not move.

[innov8]

Yes. The tool rotates the cylinder...

The tool worked... with much effort on the passenger side (see picture in previous post). The passenger side took about 2 hours of turning, cleaning the piston and drenching it with penerating oil and turning again. The piston would only move about a 1/4 turn every 15 minutes or so until it was almost completely retracted. The last rotation was the only full turn that was what I would call 'easy'. During all of this the hand brake is off and the master cylinder cap is removed.

Now I am looking at the car, 1/2 completed and the caliper on the driver won't move at all...even with the most aggressive pushing and prodding. It simply won't move...even when stepping on the brake...it doesn't move out.

Any tricks or suggestions on how to get the cylinder moving with the special tool? ...or do you have a link to a tech article on replacing the caliper. Any advice would be great. Patrick

[innov8]

I was just re-reading the tech article for replacing the pad and rotors above...maybe I missed something...anyway, I realized that I haven't a clue what this is...

"A VAG-COM IS NEEDED FOR VEHICLES EQUIPPED WITH ESP"

My S4 has ESP... what is a VAG-COM? When bleeding the brakes, I plan on using a vacum bleeder that I use with my 911sc. It works well and eliminates the assistant.

One thought related to the stuck caliper cynlinder...could it be related to a brake equalizer (balance) valve. Do these Audi's even have this valve to balance the brake load between front and back? Could the stuck cylinder be pressure build-up in the lines? Should I try opening the bleeder value while turning the tool? Any thoughts?

Thanks again.