Quattro UR need to change brake master cylinder

jossdawn · 30-08-17, 07:11 PM

Hello

Can anyone advise me on how to exchange my brake master cylinder on my 1985 Quattro UR
I know its not a straightforward process but any photos or advice will help.
Thanks

wall

Hanuman · 30-08-17, 07:41 PM

On the contrary. I think it took me under two relaxed hours, including a full fluid change while i was at it.

I'll see if the Bentley manual is to hand, but It really was as easy as it looked. In my case, the slowly locking front brakes precipitated the change.

Things that I was concerned about before i started.
Reservoir. 30yr old plastic reservoir, could be fragile. Luckily, it wasn't. But being careful how it was removed from the master cylinder. Basically, gently pressing it off without twist or bending the two spigots. Equally, I was interested in preserving the rubber grommets, even though the new cylinder had two. (Useful spares)
Brake pipes and bleed nipples. the usual thing, making sure they can be undone, and having spares in case they get fubar'd in the process.

Parts needed.
In my case, plenty of brake fluid, and a new master cylinder.

Tools
⅜" socket set. usual suspects
Brake bleed kit- Jam jar with a hole, and long hose to drain the fluid
Broom stick (if the mother in law is still off travelling, any stick long enough to press the brake pedal)

(Bentley manual prompts to deplete the system pressure with the old 20 presses of the brake pedal before starting)
I used the opportunity to check the bleed nipples as the moment to drain the fluid down (all the brakes and been worked on in recent times, anyway) until the reservoir was empty, but not completely emptying any lines.
Lots of rags under the master cylinder to catch the dribbles.
Removed the reservoir from the old cylinder- straight upwards, with as even an amount of pressure applied at both ends. It was tight, but not excessively so. I've heard of folks having trouble here, but then, this is the second cylinder in 25 years. so it's been freed off before.
Separate the lines and removed the old cylinder. But not the booster. Bentleys manual makes a not not to pull the shaft out of the booster.

Reassembly being a reverse process.
Then bleeding the brakes, I actually pumped through quite a bit of fluid to be sure of a complete fresh charge.
Bentleys lists the bleed sequence as-

Booster
Right rear
Left rear
Right front
Left front.

It seems a more daunting task that it really is.

Little pic, which constitutes all the visual instructions that you'd see in the manual.

I think I've covered the main points��

jossdawn · 31-08-17, 05:58 AM

Hi Thank you for your response on this matter this particular car does not have a servo it has an accumulator with the master cylinder connected directly fitted to the brake pedal I need some information in exchanging the cylinder on that particular model thanks.

John. · 31-08-17, 06:10 AM

Are they not all the same......."hydraulic booster" as above?

Colin Aitchison · 31-08-17, 08:32 AM

Yes it dose sound quite straight forward, I have replaced my brake master cylinder on my 1985 Ur quattro with ABS, after having 3 goes at bleeding the system and still having a brake pedal going to the floor, the advice I was given was to bleed 500ml of brake fluid through each caliper bleed nipple, yes this dose sound daft and a lot of fluid and you really can't do this with pumping the brake pedal you need a brake pressure bleed kit but this method worked for me, the pressure kit normally works from your spare tire, unless you have a very good seal between you brake master cylinder reservoir cap and test kit do not use a spare wheel with 30+ psi pressure because it pops off and you have a brake fluid mess to clean up, I did use the adjustable output from my compressor turned down to under 5psi, and now use it as my standard one man bleeding method, it dose save the mother from whingeing about her sort right knee the next day. Tip of the day, it may seam obvious after reading this but every one has done this at some time or seen it done, you pick up your 1Lt bottle of brake fluid you got the other day from the motor factors and give it a shake to make sure it is mixed,
DON'T, I did and got a kick in the arse many many years ago, just thought I would share.

Hanuman · 31-08-17, 09:17 AM

Quote:

Originally Posted by jossdawn

Hi Thank you for your response on this matter this particular car does not have a servo it has an accumulator with the master cylinder connected directly fitted to the brake pedal I need some information in exchanging the cylinder on that particular model thanks.

Correct (mostly), except that the master cylinder is mounted on the booster, which provides the servo function, rather than a vacuum servo that most folks might be familiar with.
- as John points out; standard, all the quattro turbo has essentially the same setup. The info I have given is for a quattro. Mine is a 1985 WR.

Here are a few pics with all of the major components.

Overall-

Master cylinder

Servo/Booster

jossdawn · 31-08-17, 03:01 PM

Thanks for the layout

Someone mentioned that the way to exchange the master cylinder on my 1985 UR is to completely remove the pedal box has anyone attempted changing the master cylinder by this method.

Hanuman · 31-08-17, 03:20 PM

That's the clutch master. That is a sod, but can be done in situ if you are relatively dexterous and flexible-

Clutch pedal and Clutch master/slave components.

The clutch master cylinder is directly forward of the clutch pedal. I've swapped one in under a couple of hours, before. It requires lying on your back in the footwell.
Two retaining bolts (¼" drive ratchet, plenty of salty water for your tear ducts when you bang your knuckles).
Feed from the reservoir, output line to the slave.

All of the brake master components are in the engine bay, between the Main rad and the firewall.

Like this-

30-08-17, 07:41 PM	#2
Hanuman Trickster Classic Audi Club Member Join Date: May 2009 Location: Heckling from the cheap seats, Phnom Penh, KoW Posts: 7,006	Quattro UR need to change brake master cylinder On the contrary. I think it took me under two relaxed hours, including a full fluid change while i was at it. I'll see if the Bentley manual is to hand, but It really was as easy as it looked. In my case, the slowly locking front brakes precipitated the change. Things that I was concerned about before i started. Reservoir. 30yr old plastic reservoir, could be fragile. Luckily, it wasn't. But being careful how it was removed from the master cylinder. Basically, gently pressing it off without twist or bending the two spigots. Equally, I was interested in preserving the rubber grommets, even though the new cylinder had two. (Useful spares) Brake pipes and bleed nipples. the usual thing, making sure they can be undone, and having spares in case they get fubar'd in the process. Parts needed. In my case, plenty of brake fluid, and a new master cylinder. Tools ⅜" socket set. usual suspects Brake bleed kit- Jam jar with a hole, and long hose to drain the fluid Broom stick (if the mother in law is still off travelling, any stick long enough to press the brake pedal) (Bentley manual prompts to deplete the system pressure with the old 20 presses of the brake pedal before starting) I used the opportunity to check the bleed nipples as the moment to drain the fluid down (all the brakes and been worked on in recent times, anyway) until the reservoir was empty, but not completely emptying any lines. Lots of rags under the master cylinder to catch the dribbles. Removed the reservoir from the old cylinder- straight upwards, with as even an amount of pressure applied at both ends. It was tight, but not excessively so. I've heard of folks having trouble here, but then, this is the second cylinder in 25 years. so it's been freed off before. Separate the lines and removed the old cylinder. But not the booster. Bentleys manual makes a not not to pull the shaft out of the booster. Reassembly being a reverse process. Then bleeding the brakes, I actually pumped through quite a bit of fluid to be sure of a complete fresh charge. Bentleys lists the bleed sequence as- Booster Right rear Left rear Right front Left front. It seems a more daunting task that it really is. Little pic, which constitutes all the visual instructions that you'd see in the manual. I think I've covered the main points�� __________________ I wish they would keep the damned Chinese away now that I can go home, so that I can enjoy Fish amok and a draught Angkor Last edited by Hanuman; 30-08-17 at 08:37 PM.

31-08-17, 03:20 PM	#8
Hanuman Trickster Classic Audi Club Member Join Date: May 2009 Location: Heckling from the cheap seats, Phnom Penh, KoW Posts: 7,006	Quattro UR need to change brake master cylinder That's the clutch master. That is a sod, but can be done in situ if you are relatively dexterous and flexible- Clutch pedal and Clutch master/slave components. The clutch master cylinder is directly forward of the clutch pedal. I've swapped one in under a couple of hours, before. It requires lying on your back in the footwell. Two retaining bolts (¼" drive ratchet, plenty of salty water for your tear ducts when you bang your knuckles). Feed from the reservoir, output line to the slave. All of the brake master components are in the engine bay, between the Main rad and the firewall. Like this- __________________ I wish they would keep the damned Chinese away now that I can go home, so that I can enjoy Fish amok and a draught Angkor Last edited by Hanuman; 31-08-17 at 05:07 PM.

31-08-17, 05:58 AM	#3
jossdawn Newbie! Join Date: Aug 2017 Posts: 11	Hi Thank you for your response on this matter this particular car does not have a servo it has an accumulator with the master cylinder connected directly fitted to the brake pedal I need some information in exchanging the cylinder on that particular model thanks.

31-08-17, 06:10 AM	#4
John. 4 ring whore! Classic Audi Club Member Join Date: Mar 2011 Location: Scottish Borders. Posts: 7,520	Are they not all the same......."hydraulic booster" as above?

31-08-17, 08:32 AM	#5
Colin Aitchison Senior Member Classic Audi Club Member Join Date: Dec 2013 Location: Back home in Tillicoultry Posts: 1,308	Yes it dose sound quite straight forward, I have replaced my brake master cylinder on my 1985 Ur quattro with ABS, after having 3 goes at bleeding the system and still having a brake pedal going to the floor, the advice I was given was to bleed 500ml of brake fluid through each caliper bleed nipple, yes this dose sound daft and a lot of fluid and you really can't do this with pumping the brake pedal you need a brake pressure bleed kit but this method worked for me, the pressure kit normally works from your spare tire, unless you have a very good seal between you brake master cylinder reservoir cap and test kit do not use a spare wheel with 30+ psi pressure because it pops off and you have a brake fluid mess to clean up, I did use the adjustable output from my compressor turned down to under 5psi, and now use it as my standard one man bleeding method, it dose save the mother from whingeing about her sort right knee the next day. Tip of the day, it may seam obvious after reading this but every one has done this at some time or seen it done, you pick up your 1Lt bottle of brake fluid you got the other day from the motor factors and give it a shake to make sure it is mixed, DON'T, I did and got a kick in the arse many many years ago, just thought I would share.

31-08-17, 03:01 PM	#7
jossdawn Newbie! Join Date: Aug 2017 Posts: 11	Thanks for the layout Someone mentioned that the way to exchange the master cylinder on my 1985 UR is to completely remove the pedal box has anyone attempted changing the master cylinder by this method.