UrS4boy

First, the relevant UrS4/S6 part numbers:

<img src="http://12v.org/urs/RearBrakePNs.jpg">

For me, this began in January 2004 when I discovered my 93 UrS4 had a siezed right rear caliper. At the time, the UrS4 was my daily driver so it was imperitive that I fix it. I followed a <a href="http://12v.org/urs/FredMsAudiUrS4E-brakeCamRehabDIY.pdf"> procedure written by Fred Munro</a> to try to "rehab" the emergency brake cam/lever and avoid the total replacement. Didn't work for me and <a href="http://www.20v.org/brakere.htm">THIS rear caliper overhaul procedure</a> wasn't around at the time.

So it was either buy new or reman'd calipers (new PN 447615423 - right, 424 - left (Note: Check these PNs with the dealer because odd numbers usually = left)) and make the swap.

My dealer had no UrS rear calipers in stock (1 week delivery) so I bought a reman'd right rear caliper "made" by Fenco for $115 (CDN) (C8484 = right, C8485 = left). It was excellent. In fact I can't really believe it was a reman. It looked brand new from Girling. The only difference was some coloured epoxy over the VW-Audi info. I installed it with little or no instructions sitting in my cold garage. I liked the caliper so well, I went and bought the left rear, including a $110 (CDN) core charge. Unfortunately, I never had to install it (left caliper was working fine). But today (which was Oct. 25, 2009 at time of first writing). I decided I should install it so the caliper ages aren't too far apart and so I can get my core charge back. Of course, I forgot all those tricks I "learned" the first time. So I thought I would share what I relearned. (The additional comments are as of today (Dec. 2, 2013))

First note: Fenco is gone, replaced by Cardone. I have no idea about quality.

Another Update: In January 2007, I did the rear brakes on my 98 C4 A6 quattro avant when I imported it from the US to Canada. They weren't pretty and I didn't want to fail inspection over rear brakes. They are basically the same as the UrS4 except solid rotors and different calipers. This past weekend (Nov.30/Dec.1/2013, I replaced the 2007 calipers and rotors, using my memory and the Oct. 25, 2009 suggestions.

Note, if you think you are having (or might have) emergency brake cable issues, you might also want to read <a href="http://forums.quattroworld.com/s4s6/msgs/24448.phtml">this e-brake cable post</a>

Here are the steps I used all three times (YMMV, take all necessary precautions):

1. Put car in gear, release the emergency brake, block front wheels.

2. Remove wheel bolt cover, and loosen all five rear wheel bolts (17 mm socket counter-clockwise (duh)).

3. Jack up the rear wheel. I used my little hydraulic trolley jack under the rear A-arm.

4. Remove wheel bolts and wheel. Place them away from the immediate work area.

5. Block car as required for protection in the event the jack ceases to function.

6. Note how the brake line and emergency brake cable are oriented. (I forgot to even think about this the first time - as you will see - it "bit" me later)

7. Spray the pertinent connections with WD40, Liquid Wrench (my goto) and/or PB Blaster asap to give them time to soak in. This will include the brake hose connection at the caliper, the Item 4 and 5 guide pin bolts/pins and the Item 6 caliper carrier bolts (both ends of that one (inner and outer))

8. Try to loosen the brake line at the caliper (14 mm open-ended wrench). If you can loosen it, snug it up gentley again. If you can't, spray some WD40 or Liquid Wrench(tm) (or PB Blaster) on it. Wait a bit, tap it lightly and try again. Repeat until you can loosen the hose and then snug gently. (You need to have broken it loose before you actually get to the step where you swap in the new/rebuilt caliper).

9. Loosen the carrier bolts (Item 5 in the diagram above). The head of the bolt is 13 mm but you also need to hold the carrier pin (Item 4) with a thin 15 open-ended wrench. Remember you are working backwards and figure out which way is "loosen" before you go at it. You might need a 13 mm socket and a bit of breaker bar to get things started.

10. Remove the carrier bolts and swing the caliper away from the rotor. Rest on the A-arm with the emergency brake cable and brake hose still attached.

11. Remove the pads from the carrier. If you are reusing the pads, note which one is the inner and which one is the outer. Place in a safe clean dry nearby location. If there isn't much pad left, replace with new pads (and rotors if they are bad). Mine were fine the first time. The rear brakes really don't do very much work. But they do some and that's important.

12. Twist the caliper around gently and remove the emergency brake "ball" end from the emergency brake cam lever. To do this, place a broad-bladed flat head screw driver in the return spring (Item 1A) hole and twist to release the pressure on the ball end of the cable. Push the ball end toward the caliper body until it clears the slot in the cam lever. (This can be a bit tricky, I ended up removing the return spring entirely so the "twist" was easier). UPDATE: Definitely easier if you remove the spring before even trying to remove the eBrake cable. A special 10 mm bolt holds the spring pin on. I used a 10 mm 6 point deep 3/8" drive socket.

13. Remove the clip that hold the emergency brake cable into the caliper. Note how it is oriented (with the loop end away from the caliper and the open ends towards the caliper). Use a screw driver to pry the spring away, as required. Place in a safe place for later reuse.

14. Remove the the emergency brake cable from the caliper. It may not want to pull out easily because of corrosion. I used a little WD40 (or Liquid Wrench or PB Blaster) and some light tapping before it would come loose.

15. Inspect the cable end and rubber boot. On the one I did in Jan. 2004, the boot was on wrong (!!). The fat end should be away from the ball and the narrow end should be up against the ball. Apply never-seize to the exposted part the of the cable. Fill the boot with some as well.

16. Bring the new (remanned) caliper close by. With some rags handy to wipe up any spills, loosen the 14 mm caliper brake hose fitting just enough so it is loose. Spin the caliper off the hose (yep, you heard me, spin the caliper). The hose can't take the wind-up that would be needed to ge the hose out of the caliper. Easier to wind the caliper off the hose. (NOTE: This is kind of a cheat and it is not best practise. However, if the hoses are in good shape, it avoids issues at the connection between the rubber hose and the hard line at the body. Snapped hard lines due to corrosion will NOT make your day.)

17. Put the old caliper down with the hose connection end up (so it won't drain on your nice garage floor) and quickly grab the new caliper.

18. In a reverse of the removal, spin the new caliper onto the hose (making sure that you aren't cross threaded). Keep spinning until you are pretty tight. Snug the fitting with the 14 mm wrench. Lay the caliper (without the ebrake cable so far on the A-arm).

19. If you want to replace the rotor, this is the time. The proper UrS rotor (Item 9) is 269 mm dia x 20 mm thick (ventilated) PN 857615601.) To do this, you need to remove the carrier by removing the two Item 6 Allen head bolts usig a 6 mm allen head socket. Clean out the inner part of the bolt heads if you can't get the allen socket tip in very far. You might need to use a breaker bar to get things started.

20. With the carrier off, remove the guide pins from the carrier. Before you do, wipe the crud off the rubber bellows, especially at the end closest to you. Pry (gently) the rubber bellows off the carrier (closest to you) and pull the pin towards the car (away from you).

21. Clean the pins and apply neverseize (or your favourite appropriate grease) and re-install. Make sure that the rubber bellows end closest to you "clips" over the ridge on the carrier. (NOTE: IF the bellows have a rip, you should replace them before proceding with the remaining steps).

NOTE: On this most recent go (Dec. 1, 2013), one of the guide pins was bent somehow. Would have been a weekend project show stopper but I happened to have new replacement guide pins with new rubber boot and hardware.

Clean up the carrier as much as you can. This includes the area where the metal pad backing contacts the carrier. Metal files and/or wire brushes are your friends.

22. Remove the old rotor if you are replacing it. Clean off the hub with a wire brush to remove any rust etc. I applied a very very thin wipe of never sieze on the face of the hub before installing the new rotor (or replacing the old rotor for that matter).

23. Reinstall the carrier over the edge of the rotor. Make sure that you get the orientation correct. I reused the allen head bolts and applied some blue (removable) Loctite to the first six or seven threads of the bolt (at the tip end). Not sure of the torque. Goodandtight. (No room for a torque wrench if you are doing it on jackstands).

24. Now, this is the step that I "Doh'd" out on the first time: Trial the caliper up against the guide pins. IF the brake hose is too twisted, rotate the caliper until the the hose is not as twisted (I forgot to do this the very first time and had the emergency brake cable back on and was snugging the the carrier bolts before I noticed the extra twist in the brake hose. D'oh!! (Merde). There was only one cure - remove the carrier bolts, and the emergency brake cable and untwist the hose by rotating the caliper). Once you are happy with the caliper and hose orientation, rest the caliper on the A-arm - don't let it hang on the brake hose.

25. Push the emergency cable through the hole in the caliper. Re-install the clip (looped end to the car, open ends to you).

26. Reinstall the ball-end of the emergency brake cable in the new caliper's lever arm. Twist the arm with a big screwdriver in the spring slot and pull the ball end until it slips into the cable groove in the lever arm. (If this proves difficult, remove the return spring, get the cable in place and then re-install the return spring). NOTE: This time (Dec. 2013), I just remove the 10 mm bolt holding the spring on when I took the eBrake cable off so re-installing the eBrake cable in the new caliper was easy. To re-install the spring, install the spring with the 10 mm bolt with the looped end in the groove of the bolt. Then use water pump pliers (opened about 1.5") and squeeze the spring so you can get the other end of the spring into the slot in the eBrake cam.

27. Return the brake pads to their former inner / outer position (or install new pads, Item 20, PN 4D0698451A, if required). Note: the pads should have "rabbit ears" springs - if they don't they are the wrong pad. If you are installing new pads, you will need to wind the piston back into the caliper using a <a href="http://www.denlorstools.com/home/dt1/page_6504/rear_brake_caliper_piston_tool_set_kd_41540.html"> caliper piston tool first)</a> New calipers will probably come with the piston already turned in.

NOTE: I have found recently that to get the pads to fit in properly with a tiny bit of clearance in the caliper carrier, I have had to file the metal of the pad backing on every pad that I have installed even OE pads from the dealer. Not sure why.

28. Install the caliper into the carrier. Use blue Loctite(tm) to ensure that the bolts don't loosen. Start the top bolt by hand and then the bottom bolt (there will be a bit of stress here because you have to rotate the bottom of the caliper forward to compress the pad springs). When you have both bolts started, use the 13 mm wrench/socket on the caliper bolts while holding the carrier pins with a thin 15 mm open-ended wrench.
I didn't have a torque setting so I just got them as tight as I could with my long handled wrenches. (Please check the torque settings).

29. Remove the rubber bleeder screw cap and loosen the new bleeder screw with a flare wrench (might be 11 mm for the UrS4/S6 calipers (it was 10 mm for the C4 A6 calipers). Put a hose over the bleeder screw and run into a glass container. Bleed as normal ( Pressure bleeders are best. I used a one man bleeder and many many slow short brake pedal strokes to fill the caliper and then remove any bubbles). NOTE: Monitor the master cylinder and don't let it go dry. I used Pentosin Super DOT 4 brake fluid to refill.

30. Tighten the bleeder screw and install the rubber cap. Wipe up any fluid dribbles.

31. Move tools away and reinstall the wheel. Snug wheel bolts.

32. Remove blocks etc. under car and lower the car on the jack until the jack can be pulled clear.

33. Tighten wheel bolts in a star pattern (82 lb ft) in the normal fashion.

34. Clean up your work area and store tools appropriately.

35. Pump the emergency brake handle a few times to move the piston out on the new caliper.

36. Check the level in the master cylinder. Top up with Pentosin Super DOT 4 (or equivalent).

37. Test drive. Gentle stops at first.

38. Return home. Park. Get beer. Sip. Guzzle. Belch.

39. Pat yourself on the back for a job well done.

HTH

YMMV

Dave F.