Audi A6 2008 one pad wearing quickly at rear

[Strath44]

Hi Folks I have a 2008 A6 2.0 tdi bre with E brake.

the passenger side inside (hidden pad) has worn down to the shim / back plate and is now grinding against the disc - the disc is shot.

The other pad on the outside has about 3mm wear left and the other side of the vehicle pads have about 4mm.

My assumption is that the passenger side caliper is sticking, is this something I can sort or will I need a replacement caliper?

(having a look it seems like I need a new caliper if anyone knows the spec for this car or has one for the rear P/S they want to sell let me know).

I need to fix this fairly soon as it sounds terrible when breaking, not that safe, metal filings sticking to wheel as well!

Any feedback appreciated!

[dan2485]

Have you got VCDS or a similar tool as you need this to service the brakes.

You can get replacement pistons and seals along with new slider pins if your confident in replacing this.

You need to inspect the calliper to see if the sliders are ok or if the calliper piston is sticking.

If if you don't want to do this then it's a new calliper.

My my right rear calliper is doing this also, just got to inspect the pads regularly.

I just bought a piston kit around four hours ago.

[Strath44]

Yes thank I have Rosstech - was a needed as I have a Passat B7 as well.

I had same symptoms as you well mainly accelerated wear on this inner pad - I last did the rear pads on 26th Nov 2016 so they have almost done a year. With it being out of view and my wives car it is hard to monitor.

How long are you getting from your pads normally?

I'm a bit worried about doing the rebuild kit, couple of reasons; in the past I've found that in this situation with other cars the piston has a bit of corrosion which mean replacing that as well. If it doesn't work the car which is a daily would be out of action and Rosstech recommends keeping the car hooked up to a 12v supply throughout (which I do with a smart charger).

What's your thoughts,

I tried ECP and car parts for less and looking about 180 - 225 for a replacement or a cheap German on on ebay for £130!

I need to change the fluid as well, any special procedure you follow?

[swalker]

3 or 4mm why were they not changed before this? New pads discs strip inspect and clean the sliders.

[Strath44]

Dan can you post a link to where you got the rebuild kit was it just ebay - I tried GSF and ECP they don't do them anymore. I'm pretty sure I'll need a piston as well.
I have worries about undoing the bleed nipple if I go down the rebuild route.

My sliders were fully cleaned, inspected and greased with pagid lubrication (ceratec) on the last build in Nov 16 so certain its not the sliders and more likely a sticky piston.



3 or 4mm why were they not changed before this? New pads discs strip inspect and clean the sliders.

Wear indicators come on on most cars at 2mm, average brake pad thickness of friction material is 12mm but varies so 3 to 4mm is leaving 1/4 to 1/3 of the pad life remaining any more is wasteful in normal operating circumstances IMO.

Have a read -

Access forbidden! (http://www.textar-professional.com/wp-content/uploads/Textar_Technical_Information_EN.pdf)

[dan2485]

theres not many left

Audi A6 (C6) (07-11) rear brake caliper repair kit & piston (Elec H/B) PK232C | eBay (http://www.ebay.co.uk/itm/Audi-A6-C6-07-11-rear-brake-caliper-repair-kit-piston-Elec-H-B-PK232C-/332344889257?hash=item4d614c8fa9:g:YJAAAOSwfcBZkxA t)

or

http://www.ebay.co.uk/itm/Audi-A6-C6-2004-2011-Rear-brake-caliper-repair-kit-piston-Solid-disc-PK138MK/332258331866?_trkparms=aid%3D222007%26algo%3DSIM.M BE%26ao%3D2%26asc%3D46150%26meid%3Dbce13fdee0a9462 7a32f239b3824fbf2%26pid%3D100623%26rk%3D2%26rkt%3D 6%26sd%3D332344889257&_trksid=p2047675.c100623.m-1

[Strath44]

Thanks I got the PK138 variant with 41mm piston for my 1kd brake system in case anyone is interested.

On Friday night I will have a look and see if I can crack the bleed nipple and general state of play. If all is well I'll remove the calliper and change the seals on it. I noticed that a German kit comes with various other parts inc a bearing race I'm hoping that from past experience mine just has a rusty piston and damaged front seal.

If anyone knows any rebuild posts or videos for calipers with epb please let me know.

Any thoughts appreciated

[dan2485]

when you take the caliper out take the motor off the back of the caliper and inspect the condition of the splined teeth on the drive for wear.

Also unscrew adjuster and clean up the threads.

http://i.ebayimg.com/images/g/IJQAAOSwutFZf2Z-/s-l1600.jpg

http://i.ebayimg.com/images/g/ieAAAOSwVGhZf2Z-/s-l1600.jpg

There are plenty of posts on the YouTube

This one is very good Brake caliper rebuild - YouTube (https://www.youtube.com/watch?v=rf-ONbg9-os)

[dan2485]

This is a good page

TRW Electric Parking Brake EPB - KPS Automotive Parts (http://kpsautomotiveparts.co.uk/trw-electric-parking-brake-epb/)

[Strath44]

Thanks for both those links. I think that the thing that will probably grind me to a halt is the bleed screw and other bolts such as the motor ones!

[dan2485]

If you do get stuck the nipple is a M10x 1mm pitch.

The motor bolts are M8x22 T30 cap head bolts.

If you take off the motor you should be able to wind the piston fully out with the adjuster.

The piston just sits in the adjuster, remember to fully wind it back in on the rebuild and carryout the calibration/function test with VCDS on refit.

[Strath44]

Thanks Mate,

ok so everything was seized completely and to cap it all off the key snapped in my garage door!

on the plus side I eventually freed off the bleed nipple and the bolts on the guide pins also there is indeed a tear in the piston boot!

tomorrow I will run vagcom and release brake to remove calliper.

i will need a bleed nipple which is a worry on a Saturday but the current one is ok I guess in the mean time (can you grease them to prevent seizing?)

when you talk about winding the piston out does that avoid having to run air through it to pop out the piston?

normally I have my smart meter charger attached throughout any brake repairs, do I leave the motor cable connected and just remove the motor?

[dan2485]

If you have freed of the nipple it should be fine.

The caliper is very simple there should be no need to use any air to push out the piston, just wind the adjuster out with the motor off.

You may need to unclip the boot on the piston.

if its stuck in then you need to pressurize some fluid to get the piston out.

Im doing mine on sunday, If you are renewing the small O ring on the adjuster then once you release the C clip lift the caliper off the adjuster and do not pull the adjuster out of the caliper as the roller bearing is at risk of falling apart.

Remember to clean the caliper properly and use emery cloth to remove any high spots of rust.

As long as you turn the ignition key to off then you can remove the caliper whole but do leave the charger attached and clear any faults when done and run the calibration once the parking brake has been set to close.

[dan2485]

P.S. clamp the brake hose before you start and top up and bleed the brakes when the job is done whilst looking for any leaks.

[Strath44]

thanks that's a big help!

just to clarify,
I can unwind / release the epb with vcds as per usual
Then clamp the brake fluid line
remove the caliper
Remove the motor
Wind out the piston

upon re-fitting the piston i take it I fully wind back in the adjuster then fit the new piston & boot

I would normally finish the standard pad job by closing the epb via vcds, does the motor and epb module relearn the position of the adjuster within the caliper - ie as long as i fully wind it back in upon refitting the motor it should be ok?

[dan2485]

All of the above is correct

The calibration/functional test aligns the brake properly.

[Strath44]

hey, bit of an update!

I ended up taking the caliper off the car as it was going to be ten times easier to work on!

I had to unscrew the brake hose at the caliper as the upper connection looks very rough!

got the caliper off, both torx head motor bolts snapped which is a pain, i hope i can drill them out but a bit sceptical.

thanks for the tip on winding out the piston that worked perfectly and everything cleaned up well, I ended up taking everything apart as I was worried about dirt.

i assume the brake fluid lubricates the bearing race? is there any grease I can use for assembly?

Going to try penetrating fluid then heat on the snapped bolts tomorrow I have a cheap pillar drill so that will be next, any tips or suggestions appreciated!!!!

[dan2485]

You know what your doing with the drilling out and then run a tap through the holes.

I' m going to do mine today, I have a feeling that I have the wrong piston kit as the piston that I have is 42.8 mm.

I have like you a 1KD rear caliper.

I will measure my one on the car before I take it apart.

I went on the year of manufacturing of the car.

Thanks for for the update.

[dan2485]

Yep the wrong kit, so a new p138 kit ordered. Will do it next weekend.

[dan2485]

how did you get on today?

[Strath44]

Good thanks again for all the advice.

The torx head bolts that snapped were a PITA I heated them and tried an extractor but it wouldn't work - in the end I drilled them out and although I was a bit off centre with my drilling the remaining bolt disintegrated and I was able to run 2 new 25mm m6 cap head bolts in.

I spent a long time cleaning the caliper and filing the outer surface that would contact the piston boot, the caliper is pretty rusty I would love to have given it a blast in a cabinet but this tends to bring more issues than good!

I've never replaced a boot and piston before it went ok i liberally applied rubber grease to most surfaces and ensured everything was very very clean before starting, this was tricky due to rust specs but i'm pretty happy.

Car parts for less have some good discount codes just now discs, pads, air filter, wipers, pollen, fluids, cleaners, fuel filter were £180. The Frentech piston kit was £22 odd.
Very annoyingly even though I double checked the spec (mine is 1kd solid discs) the supplier gave me the wrong guide pin / sliders so I just cleaned up the old ones they were actually fine inc the boots.

Have attached the pics below!

[Strath44]

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[Strath44]

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[dan2485]

Thats good to hear.

My calipers dont look as rusty as yours, i expect to have similar issues though.

I will be plus gassing the motor bolts via the small hole each day until saturday.

[Strath44]

One thing I know for sure is cheap cheap car washes that use strong wheel cleaner / traffic film remover away from them that really speeds up rusting!

I utilised that hole and drilled it out to run a longer bolt through.

I managed to snap / break the small securing lug on the epb to caliper wiring plug it still goes on but need to secure it with something I think!

[dan2485]

A cable tie around the motor should hold on the plug.

[niall campbell]

Great thread

How much is it for a whole new caliper with electrics & how much have you guys saved ?

[dan2485]

A new caliper from the dealer £300 or a refurbed one plus returning the old one around £100.

If the motor goes they can be got for around £60 on Ebay.

[niall campbell]

ok thanks

[Strath44]

That's not bad for the dealer ecp or car parts for less were about £250 if you give over your old calliper. That was for trw as well.
ill happily go that route eventually knowing that at least I gave this a bash!

[dan2485]

Did my calliper today, everything went fine.

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The motor bolts came off easily enough. The plus-gassing worked well.

The piston on my calliper was scored and I'm hoping that this is the source of the squeaky brakes that I have been having.

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The caliper internally looked OK.

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All rebuilt and a new stainless steel bleed nipple fitted.

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If you need to know the piston size its stamped on the calliper see the 41 in the middle.

The bigger calliper has 43 stamped on the RH side.

I would recommend this before you shell out for a new calliper.

I will do the other side on the next service.

[Strath44]

well done!
mine has been running fine for 150 miles will see how it goes!