Rear caliper problems, your advice please
 

Lost brake pedal pressure and got brake pad warnings all at the same time.

Bought new pads and discs. Changed the rear right side and all went well.

Removed the caliper and disc on the rear left (near side) and saw wet fluid un the underside of the caliper. Not where the piston pushes the pad, that was dry. It looks like (need to confirm) that the fluid is leaking from where the EPB mounts onto the caliper.

Does this mean a new caliper or can they be rebuilt? What are my options?

Many thanks

Remanufactured or new caliper from the dealer is your best bet. You should be using the Ross-tech or VW/Audi software & diagnostic interface cable to correctly set the rear calipers.

I would go http://www.ebay.com/itm/2004-2010-AUDI-A8-D3-4-2L-QUATTRO-REAR-BRAKE-CALIPER-SET-OEM-/251591074082?pt=Motors_Car_Truck_Parts_Accessories&hash=item3a93ff2122&vxp=mtr.

Pretty easy to rebuild... BUT, notice last part on other possibles
 

...if you are familiar with most anything internal hydraulic brakes, or even basic moving piston stuff. Audi (or Ate) has always had a basic seal rebuild kit for most any Audi I have ever owned, whether front or rear.

Here it is on the D3, with a picture: http://www.ecstuning.com/ES263054/ Here it's from ECS, but w/ the Audi part # if you look carefully and just want to get from audiusaparts, genuineaudi, etc. It is actually a listed VW part for a Phaeton too in case you want to get via a VW source.

The one question I was unsure of from the OP is you say it wasn't near the pad area but rather the EPB. I'm not sure I can resolve that, unless either I dont know the internals of an EPB, or the caliper is actually cracked at the cylinder wall (probably like a one in a million corner case). More likely it would be the internal seal you see in the picture if it is internal caliper related.

OR, it is actually NONE of the above or focus so far, but actually either just a slightly loose or corroded bleeder screw, or a deteriorated rubber line or end fitting. If the line is non OE by chance (braided, "teflon," etc.) I would scrap that as a likely suspect. Otherwise look critically at this basic stuff before even rebuilding. Often stuff big enough to leak the main piston seal can be felt as a marginally sinking pedal; the tiny leak at or near the hose end end or bleeder might just be a marginal wet look, and maybe some spots on the wheel paint (often near the spoke area) where it is eating at the wheel paint. You can buy replacement bleeder screws too, or just take them out and clean up with a small wire brush on threads and very fine sandpaper on the tapered face.

If this seal is leaking (red arrow) Brake fluid would go to the motor side and find it's way out.

Attachment 80110

Thanks guys. An update since my last post.

Sorry, I forgot to mention its a 2004 A8 4.0 Diesel.

I had a low pad warning before the loss of brake pressure, so I thought while I take it apart to look at it I'd do a disc and pad change on both rear wheels.

Done the offside no problem.

The nearside is when I noticed the fluid. As a test since my last post and while I had the caliper free from the disc, I got someone to pump the brakes and I couldnt see any fluid coming out. I dried the caliper off and repeated and syill no fluid. So I blead the brakes and repeated and still no fluid.

The pads were worn, i'd say down to 1-2mm on the inside pads and 4mm on the outside pads.

So now I completed the build of new disc and pads on the nearside wheel.

I performed all the Vag EPB procedures before and after including the cycling and entering in the new pad thickness.

The result is the brake pedal pressure is back up again and a quick test drive shows the brakes to be working perfectly, except.......

I have a warning light on the dash in yellow with red lighting bolts - I assume EPB error.

When I look at the error codes in module 53 i get the codes shown below. I have read that on the older A8's you sometimes need to repeat the cycle test and adaptation test a few times before you can clear out the error codes. I have done it about 5 times but the errors remain.

I'm a little confused at the moment. Any advice or insight?

2 Faults Found:
16347 - Control Module - EEPROM Error
014 - Defective - MIL ON
Freeze Frame:
Fault Status: 11110000
Fault Priority: 4
Fault Frequency: 26
Mileage: 169736 km
Time Indication: 0
Date: 2012.12.11
Time: 10:07:07

Freeze Frame:
Voltage: 11.59 V
Count: 187

02596 - Rear Brake Pads Worn
008 - Implausible Signal
Freeze Frame:
Fault Status: 01110000
Fault Priority: 6
Fault Frequency: 1
Reset counter: 233
Mileage: 1048575 km
Time Indication: 0

Freeze Frame:
Voltage: 5.80 V
Count: 61

Not seeing brake fluid leak doesn't mean that seals are OK. You can easily get air sucked into the system and loose brake pedal. That exactly already happened. Don't leave it as is. Take out that motor and inspect for leaks. If there is brake fluid present there you have to replace the seal from my previous post. I guess that some other eBay site would be more convenient if you decide to replace the caliper. They are cheap because nobody needs them, meaning that vast majority of them are still good.

Regarding code and warning you have, it looks like your Parking Brake Module is faulty, but it could be something else too. If both sides of parking brake where not in the same position it requires quite a few open/close cycles to align them since the system doesn't have separate alignment for each side.

Filling your profile helps people to help you.

Check the field for the pad thickness--needs to report 11 mm
 

Check the field for the pad thickness again w/ VAG COM. If it doesn't say 11mm, your entry did not stick. I have had that happen before.

Is that actually your data though in the error codes--pretty plainly whack. It reports over 1 million kilometers on the pad wear code, and it doesn't agree w/ the mileage from the other error; somehow it grabs a 5.8V signal too. Anyway, try re setting and maybe also making sure the battery is decently charged. Weird stuff happens throughout the car electronics if the battery is quite low.

It may be the first one that is actually the scarier error--EEPROM error in the control module and a frequency count already of 26, going back a few years if your clock is set right. Again though, look to see if thickness coding actually stuck, make sure system voltage is up to snuff, and clear the codes again.

Thanks guys.

On the error codes, I had a battery charger attached while I was doing the Viag stuff.

So should I re-attach the battery charger and keep to cycle test 007 in basic settings?

In my pad thickness I entered 12mm. When I went back in there it did say current value 12mm so I think that stuck.

On the fluid problem, I agree something must be wrong as you dont just lose pressure for no reason plus the caliper was wet with fluid. Are th motors easy to remove? I think I say a couple of allen head screws while I was in there. Do I jsut removed those and pull it off?

It is easy. Just those Alan bolts. Do it ASAP. Don't wait to lose it again. It could be bad moment for that.