Rear Discs & Pads - Help!

[ninjag]

Changing discs and pads all round today, fronts went fine but had trouble with the rear.

I released the handbrake and used my icarsoft tool to retract the caliper pistons and I could hear this happening. After 60 seconds I got to work on the rear n/s, however, the rear piston didn't seem fully retracted, in fact it looked like it hadn't retracted at all, so I couldn't get it back on with the new pads and discs.

I removed the EPB and tried to manually retract using the torx that the EBP would use, but nothing was happening. I did note it was already at the fully clockwise position indicating it should be fully retracted. The icarsoft was still connected, but I don't think that would matter because the EPB was removed, so it should just be a purely mechanical operation. I couldn't get it to budge though.

Could the caliper be stuck or knackered? I put the original disc and pads back on and managed to slide the caliper back on. I then used icarsoft to close the rear calipers and it went ahead and made the noises. I went round and watched and I could see the caliper and EPB move, so something was happening which then makes me think it isn't knackered.

Any advice would be greatly appreciated as my pads have about 2mm left and the discs are done as well.

 

[NHN]

Sounds like its stuck mate, strip & release to inspect, then if it moves freely, lube up & refit, test.

 

[ninjag]

Sounds like its stuck mate, strip & release to inspect, then if it moves freely, lube up & refit, test.

Strip as in remove the caliper and get it on the bench? Cheers.

 

[PenttisHSR]

You still need to squeeze the piston back into the caliper in the normal way using the old pad (but with no screwing/twisting).
Retracting the handbrake DOES NOT PULL the piston back - it only pushes!
If the centre torx is fully clockwise, then it is fully retracted, do not force it. Then you squeeze the piston back to meet it using a clamp or waterpump pliers or whatever method you like. A proper tool is not expensive, but no need to twist piston or screw back, just squeeze/push SQUARELY

 

[ninjag]

You still need to squeeze the piston back into the caliper in the normal way using the old pad (but with no screwing/twisting).
Retracting the handbrake DOES NOT PULL the piston back - it only pushes!
If the centre torx is fully clockwise, then it is fully retracted, do not force it. Then you squeeze the piston back to meet it using a clamp or waterpump pliers or whatever method you like. A proper tool is not expensive, but no need to twist piston or screw back, just squeeze/push SQUARELY

That's interesting, I did try to push the piston back with a G clamp but it wouldn't move. Didn't do it very hard though as was worried about damaging something.

So do I just need to retract the handbrake using my scan tool and then push the piston back? Come to think of it, I do remember something about being careful of the plastic cover of the EPB, I'm guessing that's when pushing the piston?

 

[audiwaterpump]

That's interesting, I did try to push the piston back with a G clamp but it wouldn't move. Didn't do it very hard though as was worried about damaging something.

So do I just need to retract the handbrake using my scan tool and then push the piston back? Come to think of it, I do remember something about being careful of the plastic cover of the EPB, I'm guessing that's when pushing the piston?

How were you trying to push the piston back?

Sound like it is stuck, and needs more force to push it back in.
I believe the rubber seal swells on these, and locks it tight.

 

[ninjag]

How were you trying to push the piston back?

Sound like it is stuck, and needs more force to push it back in.
I believe the rubber seal swells on these, and locks it tight.

Just a g clamp, but not with much force. I've seen a video though of a guy simply turning the torx (with epb removed) and this retracted the piston.

 

[audiwaterpump]

Just a g clamp, but not with much force. I've seen a video though of a guy simply turning the torx (with epb removed) and this retracted the piston.

do you have a link to that video.

 

[8YARWY]

do you have a link to that video.

Sent from my iPhone using Tapatalk

 

[ninjag]

do you have a link to that video.

About 8 mins in.

And whilst panicking I never watched the bit after when he pushes the piston in. Lol ***.

I think I've misunderstood some of the processes. So does the device (icarsoft in my case) retract the EPB (within the caliper housing) allowing space for the piston to then pushed back, or same result if doing it manually as per the video? And that unit which is removed in the video, is that just the motor and not the actual EPB? (I think this is where I've got confused).

 

[8YARWY]

About 8 mins in.

And whilst panicking I never watched the bit after when he pushes the piston in. Lol ***.

I think I've misunderstood some of the processes. So does the device (icarsoft in my case) retract the EPB (within the caliper housing) allowing space for the piston to then pushed back, or same result if doing it manually as per the video? And that unit which is removed in the video, is that just the motor and not the actual EPB? (I think this is where I've got confused).

The 1st picture in my post above is of the Motor which is bolted to the shaft.
Once it’s unbolted and removed you can then use a torx socket on the shaft to wind the piston mechanism in.

This is the other side
Below is shaft inside the moving piston cover

Use something like these to push back the piston once the inside is retracted by the motor / hand winding

Here’s the winder in situ
As it turns on the ball bearings the ‘collar’ moves up the shaft pushing the outer piston onto the pad/disc

Sent from my iPhone using Tapatalk

 

[spartacus68]

I rebuilt the calipers front a rear last year after a sticking piston on my Allroad. Audi don’t even sell a rebuild kit for the rear but you can buy from Autodoc. I chose a manufacturer call Budweg. The kit includes ‘o’ ring seals, dust cover, square seal, etc.

The dust sleeve swells with corrosion, hence the sticking piston. I had issues getting the electric parking brake off. You need long Torx 30 bits and hammer them in before removing or you risk them turning, which happened to me on one. The EPB retracts and calibrates with VCDS, but the piston remains in the same place.

With the EPB off, pump the brake to force the piston off. You can clamp the brake hose to reduce fluid loss afterwards. You’ll also need long handled circlip pliers (Nielson ones are fine). Remove the circlip and the internal mechanism can be removed. Use red grease on ‘o’ rings and the square seal. It’s a bit fiddly rebuilding the calliper and getting the circlip to sit square in the grooved recess.

With the rear calliper internals back on, add the dust sleeve to the piston and screw back on. It can’t be pushed on like fronts. You’ll need a calliper wind back tool, Draper ones are good.

Grease sliders too. Dave Sterl has a good video here.


Once the whole thing is done, ceramic grease on backs of pads, and reset electronically via VCDS or similar, then bleed the caliper. Bleed them all from furthest most caliper to reservoir. I had to do mine numerous times, but all calipers were all rebuilt on mine.

 

[audiwaterpump]

Just a g clamp, but not with much force. I've seen a video though of a guy simply turning the torx (with epb removed) and this retracted the piston.

Get yourself a proper piston wind back tool - they're not very expensive.
With the EPB in the retracted position, use the piston wind back tool to force the piston in - it will take a lot more force than you have been applying up to now.
They get stuck solid so will need some force.
G- clamp won't be any good.
This is the quickest option.

Failing that, it's a caliper rebuild job, as others have described above.

 

[rum4mo]

I remember finding and buying a second adaptor for my S-P piston retractor tool - not being posh S-P was what Halfords stocked for very little money roughly 20 years old! That second adaptor that I bought when I bought my B8 S4, claimed to be required when retracting the piston on VW Group with EPB, but I've never needed to use that yet, or if it fits this car or only maybe VW Passats - the early ones that first had EPB.

@spartacus68, I think that you mentioned that Neilsons were good enough either on here or on another forum when I enquired about rear hand brakes on Fabia/Polo, as you have mentioned this again, when I looked on ebay there were no hits when I included Neilsons, what I ended up buying, and still not needed to use, was just straight from China without any European packaging, also you called them long handled circlip pliers, I think that you meant right angled circlip pliers. I'm not trying (and failing) to be pedantic, I'm just trying to help any readers of this thread home in on the correct circlip pliers quickly - that is all!

Edit:- like this for instance https://www.ebay.co.uk/itm/265214542842

 

[audiwaterpump]

Get yourself a proper piston wind back tool - they're not very expensive.
With the EPB in the retracted position, use the piston wind back tool to force the piston in - it will take a lot more force than you have been applying up to now.
They get stuck solid so will need some force.
G- clamp won't be any good.
This is the quickest option.

Failing that, it's a caliper rebuild job, as others have described above.

Take photos and videos if you get a chance.

 

[spartacus 68]

I remember finding and buying a second adaptor for my S-P piston retractor tool - not being posh S-P was what Halfords stocked for very little money roughly 20 years old! That second adaptor that I bought when I bought my B8 S4, claimed to be required when retracting the piston on VW Group with EPB, but I've never needed to use that yet, or if it fits this car or only maybe VW Passats - the early ones that first had EPB.

@spartacus68, I think that you meant right angled circlip pliers. I'm not trying (and failing) to be pedantic, I'm just trying to help any readers of this thread home in on the correct circlip pliers quickly - that is all!

You're correct and no offence taken rum4mo long nose right angled circlip pliers.

 

[ninjag]

Thanks all, your help and been very useful. Also good to know that my icarsoft was doing the job properly so I won't have to remove the EPB motor again.

Now that I know the piston is to be manually pushed back I will have another go. I didn't realise it could be just pushed back and not rewound, every other car I've had I've had to use my rewind tool. Because I thought the EPB gear would retract the piston I didn't want to force the piston when using the g-clamp as I thought it might damage something, but now I understand what's going on I'll be able to fund out if it is just stiff or ********.

Regarding the rewind tool, I'm sure my piston had three notches in a triangular formation rather than the usual two. My adjustable rewind tool didn't seem to work. Is there a special tool for Audi? (I'm thinking like this: https://www.halfords.com/tools/hand...ton-wind-back-adaptor-3-pin---vag-209070.html although the Audi Workshop manual says to just use a piston spreader).

Many thanks

 

[audiwaterpump]

Thanks all, your help and been very useful. Also good to know that my icarsoft was doing the job properly so I won't have to remove the EPB motor again.

Now that I know the piston is to be manually pushed back I will have another go. I didn't realise it could be just pushed back and not rewound, every other car I've had I've had to use my rewind tool. Because I thought the EPB gear would retract the piston I didn't want to force the piston when using the g-clamp as I thought it might damage something, but now I understand what's going on I'll be able to fund out if it is just stiff or ********.

Regarding the rewind tool, I'm sure my piston had three notches in a triangular formation rather than the usual two. My adjustable rewind tool didn't seem to work. Is there a special tool for Audi? (I'm thinking like this: https://www.halfords.com/tools/hand...ton-wind-back-adaptor-3-pin---vag-209070.html although the Audi Workshop manual says to just use a piston spreader).

Many thanks

My wind back tool set has adapter disks, so you just choose the disk required for your car.

You did the right thing by not forcing it, as the last thing you want to do is break something. Then it starts getting really expensive.
Make sure you battery charge doesn't go low.

 

[rum4mo]

@ninjag, that is the Laser Tools adaptor that I bought via Halfords maybe back in 2013ish, still in its packaging!

I'm a bit concerned that you talk about "just pushing" and not "turning and pushing" the rear piston back in.

Also in a moment of weakness this year, for a birthday treat to my "tools" I bought one of these piston spreaders as shown in @T-1000's earlier reply, in the past I have always just used my S-P windback tool with the adaptor reversed and insert a bit of wood for it to bear on and so save the front calliper pistons from getting damaged - but now I've weakened and bought that bespoke tool - my mate just laughed " just use big screwdrivers"!

 

[ninjag]

Sorry, when I say pushing I mean specifically the piston part, rather than screwing it back, but the spreader I've bought will involve turning in order to push the plate against the piston. Near enough identical to the official Audi one, but about eleven times cheaper!

It's strange driving without any noise coming from the wheels now that the fronts are solid instead of drilled. The clunking has gone as well, which I'm thinking could have been due to the previous owner fitting cheap and poor fitting parts. I noticed the disc specs changed slightly for facelift with Brembo as well, maybe pre facelift discs were on it or something? Anyway, I'm just glad it's gone!

 

[spartacus68]

Every day is a school day Ninjag. I fitted Zimmerman discs and pads. On the bright side you’ve saved yourself some serious cash. Audi main dealer would have taken your kidney as payment.

 

[rum4mo]

Sorry, when I say pushing I mean specifically the piston part, rather than screwing it back, but the spreader I've bought will involve turning in order to push the plate against the piston. Near enough identical to the official Audi one, but about eleven times cheaper!

It's strange driving without any noise coming from the wheels now that the fronts are solid instead of drilled. The clunking has gone as well, which I'm thinking could have been due to the previous owner fitting cheap and poor fitting parts. I noticed the disc specs changed slightly for facelift with Brembo as well, maybe pre facelift discs were on it or something? Anyway, I'm just glad it's gone!

Ah, I see, but what you are using is a piston retractor not a spreader, again I'm not trying to be pedantic - the spreader does just that and it does not rotate, so perfect for front callipers and rear callipers that do not have a handbrake function, ie probably have a drum inside the disc. I'm saying this again just in case someone who has not done this sort of work reads this and dives in.
Again, the Laser Tools adaptor for piston retractor tools, it has 3 dowel pins fitted to it but also has another pattern with 2 holes, so and some rough/crude wording to the effect that implies it can be used on 3 or 2 pins configurations, so I'm guessing, dangerous I know, that I could drift out 2 or the 3 dowel pins and insert them on the other face of the adaptor and use it that way round for these B8 rear pistons, only thing is, I'm not too sure if the "2 holes" on the adaptor are the same spacing as the "2 indentations" on the pistons. Though there are a few adaptors available that have adjustable pin spacing both in 2 and 3 pins configurations, well at least Laser Tools market them.

 

[ninjag]

Ah, I see, but what you are using is a piston retractor not a spreader, again I'm not trying to be pedantic - the spreader does just that and it does not rotate, so perfect for front callipers and rear callipers that do not have a handbrake function, ie probably have a drum inside the disc. I'm saying this again just in case someone who has not done this sort of work reads this and dives in.
Again, the Laser Tools adaptor for piston retractor tools, it has 3 dowel pins fitted to it but also has another pattern with 2 holes, so and some rough/crude wording to the effect that implies it can be used on 3 or 2 pins configurations, so I'm guessing, dangerous I know, that I could drift out 2 or the 3 dowel pins and insert them on the other face of the adaptor and use it that way round for these B8 rear pistons, only thing is, I'm not too sure if the "2 holes" on the adaptor are the same spacing as the "2 indentations" on the pistons. Though there are a few adaptors available that have adjustable pin spacing both in 2 and 3 pins configurations, well at least Laser Tools market them.

Thanks for the info. This is what I bought, which I thought was a spreader? I thought a piston retractor is the one where it actually turns the piston?

Amazon product

 

[ninjag]

Every day is a school day Ninjag. I fitted Zimmerman discs and pads. On the bright side you’ve saved yourself some serious cash. Audi main dealer would have taken your kidney as payment.

Aye for sure, I avoid main dealers at all costs! lol I like to learn as much as I can about my cars but inevitably end up changing cars and having to learn all over. I'm going to have to break the habit and keep this car longer and unless something catastrophic happens I can't see any reason to change as it ticks all the boxes. I shouldn't say this, sods law and all, but so far it's been one of the most reliable cars I've had; a wheel speed sensor and a bush (a sporadic parking sensor) is all that has actually failed I think in the last 7,000 miles (hitting almost 70k now). The rest has all been upgrades, tyres or servicing.

 

[audiwaterpump]

I assume you have already invested in a digital workshop manual.

 

[ninjag]

I assume you have already invested in a digital workshop manual.

I paid for 24 hours access to some site, I forget the name but I think it's where the dealership workshops log into, and I went mental with downloading.

 

[rum4mo]

Thanks for the info. This is what I bought, which I thought was a spreader? I thought a piston retractor is the one where it actually turns the piston?

Amazon product

View attachment 252029

Yes that is a spreader typically for spreading the pads apart - it will do that by forcing the piston(s) back into the calliper, you should not use that on the rear brakes of a B8, as I said the tool that you need to use is called a piston retractor and it does rotate while pressing the piston back into the calliper, ie it screws the piston back down/along its lead screw and also applies pressure to the outer end of the piston so that it retracts back into the calliper. As others have said, the lead screw that the piston is mounted on will only force it out when turning one way, when that lead screw is turned the other way it just unscrews from the piston leaving the piston "where it started off initially before the lead screw was reversed.

 

[PenttisHSR]

Do Not Rotate the Piston!!
After winding back the motor use the SPREADER, just push the piston back. If it is done SQUARELY it will go back easy.

 

[rum4mo]

Do Not Rotate the Piston!!
After winding back the motor use the SPREADER, just push the piston back. If it is done SQUARELY it will go back easy.

So that means that the lead screw is short enough not to contact the end of the piston before the piston has been pressed far enough back into its bore to make room for the new pad?
Initially I had thought that the lead screw would be fixed to the "bottom" of the calliper piston bore, and you would need to "screw" the piston onto and down the lead screw - which of course would mean that the piston would, if you used VCDS etc, get pulled back into its "lowest" position - but reading what has been written in this thread, it seems that the lead screw actually gets moved outwards in service - is that correct and if so how does that all work?

 

[PenttisHSR]

@rum4mo I think you are getting confused with "self-adjusting" handbrake mechanisms as used on previous generations of "handbrake" cars with a cable.
What we are dealing with here is an "Electronic Handbrake"
The motor tightens the pad onto the brake disk and cuts out. When you release the handbrake it just untightens the pad and cuts out, the pistons are still held hydraulically in the normal way.
In order to replace the pads (and retract the piston all the way back) it is neccessary to fully wind back the electronic handbrake mechanism out of the way, before pushing the piston back against the hydraulics in the normal way (as was completed successfully on the front).

Latest cars then have to be re-synchronised again, but B8 is OK. Best practice would be to wind the handbrake mechanism back up to the new pad again before refitting the motor

 

[ninjag]

The workshop manual says to use a piston resetting appliance T10145 which looks like a spreader, which is why I bought one and I hope this is the right way forward? I've pasted the image from the workshop manual below. It does look like pushing the piston is the right way, but I'm also wondering why the piston has three notches in it (triangular formation) as if for a rewind tool to be used?

 

[rum4mo]

The workshop manual says to use a piston resetting appliance T10145 which looks like a spreader, which is why I bought one and I hope this is the right way forward? I've pasted the image from the workshop manual below. It does look like pushing the piston is the right way, but I'm also wondering why the piston has three notches in it (triangular formation) as if for a rewind tool to be used?

View attachment 252070

Oh well, so my newly bought spreader will find a use on the rear callipers as well as the front.

You found 3 notches on the end of the piston, oh well at least the Laser Tools adaptor I bought has that arrangement of dowel pins, but as you say - why/when is it needed! Some of the earlier pictures seem to show only 2 notches on the piston end though.

Sorry for walking you up the wrong garden path!

I can see that if I want to fully understand how these electric handbrakes and the cable handbrakes work, I'll need to strip both types of callipers down, so far I've not needed to do that.

 

[ninjag]

Oh well, so my newly bought spreader will find a use on the rear callipers as well as the front.

You found 3 notches on the end of the piston, oh well at least the Laser Tools adaptor I bought has that arrangement of dowel pins, but as you say - why/when is it needed! Some of the earlier pictures seem to show only 2 notches on the piston end though.

Sorry for walking you up the wrong garden path!

I can see that if I want to fully understand how these electric handbrakes and the cable handbrakes work, I'll need to strip both types of callipers down, so far I've not needed to do that.

It's no problem at all, it threw me and I had it all in my hands! lol Those notches.... definitely three in triangular formation because I looked at my rewind tool whilst at them and could see it wouldn't work.

Ah, I think this is similar to what it looked like:

https://www.ecstuning.com/b-genuine-volkswagen-audi-parts/rear-brake-caliper-black-right/8k0615404a/

 

[audiwaterpump]

Do Not Rotate the Piston!!
After winding back the motor use the SPREADER, just push the piston back. If it is done SQUARELY it will go back easy.

Looks like the piston doesn't need to be rotated.
As the piston isn't "connected" to anything, even if the piston did rotate would it do any harm?

 

[rum4mo]

Looks like the piston doesn't need to be rotated.
As the piston isn't "connected" to anything, even if the piston did rotate would it do any harm?

I'll blunder back in here again , if only to get educated a bit more about these rear callipers without not yet having needed to find any of this out!

So, has the piston got an internal/female thread that matches that lead screw, or is that thread on that lead screw for some other reason, although if it was for some other reason why is it threaded right up to the end as I'd think that part is fitted into the calliper body from this open end?

Edit:- one thing I'll add to your question is, when I used my S-P piston retractor on front callipers, after I've taken the calliper of its mounting, I placed a bit of maybe plywood between the crown of the piston and the rotating piston retractor tool, mainly to protect the piston from being marked from the surface of the tool adaptor, or more importantly to prevent damaging the dust/dirt seal from getting damaged, so by doing that I avoided rotating that piston while pressing it back into the calliper bore. Moving forward, as I now have a spreader, I'll just use that so the front pistons will not get rotated.

Next Edit!:- so I wonder where this leaves my S-P adaptor that has 3 dowel pins to retract VW Group rear brake with handbrake calliper pistons - or are these pistons used in another VW Group car that has cable handbrake - of the same age?

 

[audiwaterpump]

I'll blunder back in here again , if only to get educated a bit more about these rear callipers without not yet having needed to find any of this out!

So, has the piston got an internal/female thread that matches that lead screw, or is that thread on that lead screw for some other reason, although if it was for some other reason why is it threaded right up to the end as I'd think that part is fitted into the calliper body from this open end?

Edit:- one thing I'll add to your question is, when I used my S-P piston retractor on front callipers, after I've taken the calliper of its mounting, I placed a bit of maybe plywood between the crown of the piston and the rotating piston retractor tool, mainly to protect the piston from being marked from the surface of the tool adaptor, or more importantly to prevent damaging the dust/dirt seal from getting damaged, so by doing that I avoided rotating that piston while pressing it back into the calliper bore. Moving forward, as I now have a spreader, I'll just use that so the front pistons will not get rotated.

Next Edit!:- so I wonder where this leaves my S-P adaptor that has 3 dowel pins to retract VW Group rear brake with handbrake calliper pistons - or are these pistons used in another VW Group car that has cable handbrake - of the same age?

To be honest, I haven't had to do this job on an Audi yet, but I have done it on a Jap car and the piston had to be rotated whilst being pushed in. So I had assumed it would be the same on an Audi, but apparently it's not.

This may help.

How Electric Parking Brakes Work​

 

[ninjag]

I'll blunder back in here again , if only to get educated a bit more about these rear callipers without not yet having needed to find any of this out!

So, has the piston got an internal/female thread that matches that lead screw, or is that thread on that lead screw for some other reason, although if it was for some other reason why is it threaded right up to the end as I'd think that part is fitted into the calliper body from this open end?

Edit:- one thing I'll add to your question is, when I used my S-P piston retractor on front callipers, after I've taken the calliper of its mounting, I placed a bit of maybe plywood between the crown of the piston and the rotating piston retractor tool, mainly to protect the piston from being marked from the surface of the tool adaptor, or more importantly to prevent damaging the dust/dirt seal from getting damaged, so by doing that I avoided rotating that piston while pressing it back into the calliper bore. Moving forward, as I now have a spreader, I'll just use that so the front pistons will not get rotated.

Next Edit!:- so I wonder where this leaves my S-P adaptor that has 3 dowel pins to retract VW Group rear brake with handbrake calliper pistons - or are these pistons used in another VW Group car that has cable handbrake - of the same age?

Are you talking about this screw? (posted earlier by 8YARWY)

It does seem unnecessary to be screwed right to the end as I can't see it requiring to be retracted further back than that inner section. Maybe it's just easier (ergo cheaper lol) to be machined like that, or possibly it's shared with other models which require it to be fully threaded?

 

[PenttisHSR]

so I wonder where this leaves my S-P adaptor that has 3 dowel pins to retract VW Group rear brake with handbrake calliper pistons - or are these pistons used in another VW Group car that has cable handbrake - of the same age?

I found this type of tool did the job perfectly by rotating the BODY (green arrows) instead of the T-bar to squeeze the piston back. It applies perectly square pressure.

 

[rum4mo]

My original S-P version must be the same as that one, I'd need to look at it before confirming, but I never considered using it that way to avoid the adaptor turning on the piston crown - it does make sense though, my use of that on the front pistons along with a bit of plywood worked for me and kept the end of the rotating adaptor well away from the dirt/dust cover/seal.

 

[rum4mo]

Are you talking about this screw? (posted earlier by 8YARWY)

It does seem unnecessary to be screwed right to the end as I can't see it requiring to be retracted further back than that inner section. Maybe it's just easier (ergo cheaper lol) to be machined like that, or possibly it's shared with other models which require it to be fully threaded?

View attachment 252253

Yes that was what I was meaning.