A3 brake pedal travel

Red Ed

Red Ed

Registered User
Joined
Sep 2, 2012
Messages
23
Reaction score
1
Points
3
Location
NULL
I'm not sure if I have a problem or if it is all in my head.

I recently changed the front brake pads then the brake fluid, bleeding the system at each wheel whilst using a pressure bleeder at 20 psi.

My brakes feel good and they stop the car. When the engine is off the brake pedal is solid. When the engine is on I can push the brake pedal to the floor but only if I put considerable force on the brake pedal for around ten seconds. Is this normal?

I suspect it is not normal and could be worn seals in the master cylinder. Also having read the Audi workshop manuals I understand that brake bleeding pressure should be no more than 1 bar (~15 psi) or the hydraulic control unit will not be fully bled. So perhaps there is air in there after all.

Please could someone tell me if I have a problem?
 
If you have air in the system, pumping the pedal would bring the stopping point of the pedal further up. If pumping makes no difference, there is no air and the pads just need to "bed in". I put new discs and pads all round on mine this summer plus fresh fluid and yet my brake pedal didn't feel as "solid" as when I had tired discs and pads, until I did around 300 miles.
 
audi upgrades
Retroman said:
If you have air in the system, pumping the pedal would bring the stopping point of the pedal further up. If pumping makes no difference, there is no air and the pads just need to "bed in". I put new discs and pads all round on mine this summer plus fresh fluid and yet my brake pedal didn't feel as "solid" as when I had tired discs and pads, until I did around 300 miles.
Click to expand...

I hope you are right!

I get the impression there is no air in the system. But where does the hydraulic fluid pressure go when the pedal has reached the floor? Can you do this on your car?
 
as others will suggest a "long pedal" is the two nipples on the master cylinder. they need to be bled after the wheels. mine did the same when I changed the discs / pads, serviced the rear calipers, changed a front caliper for a new one and changed the fluid. once the two nipples were bled the brake pedal only travelled half way down to the floor before the brakes worked but only with the brake pedal all the way to the floor, also endangers flipping a seal if the pedal travels that far.
 
I also changed my rear callipers as one was suspect looking with a torn dust cover after having had the pads changed some time earlier by a Unipart garage. I clamped the hoses and did not let the fluid level go low in the master cylinder. I bled the system using the "two man" method and found that the rears needed doing twice with a fair bit of fluid going through - I suspect that the first bleed had been slightly too vigorous and caused some air to disperse into bubbles. My pedal did not go to the floor once the air was bled out - it just felt less firm for 300 miles.

My understanding is that the system does not like being pressure bled at more than 1 bar (14.5 psi) and that an ECU controlled valve will inhibit full bleeding above 14.5 psi. If it were me, I would get some more fluid (it's cheap enough) and methodically work my way around the 4 wheels and bleed again.
 
Full fluid change should be done every two years, including the clutch.
 
Stuart B said:
as others will suggest a "long pedal" is the two nipples on the master cylinder. they need to be bled after the wheels. mine did the same when I changed the discs / pads, serviced the rear calipers, changed a front caliper for a new one and changed the fluid. once the two nipples were bled the brake pedal only travelled half way down to the floor before the brakes worked but only with the brake pedal all the way to the floor, also endangers flipping a seal if the pedal travels that far.
Click to expand...

I've got my new master cylinder, I'm pretty sure that is the problem rather than air because I haven't introduced any air and the system has bled without any sign of air whatsoever. However now I will need to bleed my new MC.

I see those two nipples on the master cylinder. Are these the only ports used to bleed the master cylinder? In which case can I / should I do this when it's fitted on the car? Or should it be bench bled using the outlet ports as I think I've seen others doing. Confused.
 
Retroman said:
I also changed my rear callipers as one was suspect looking with a torn dust cover after having had the pads changed some time earlier by a Unipart garage. I clamped the hoses and did not let the fluid level go low in the master cylinder. I bled the system using the "two man" method and found that the rears needed doing twice with a fair bit of fluid going through - I suspect that the first bleed had been slightly too vigorous and caused some air to disperse into bubbles. My pedal did not go to the floor once the air was bled out - it just felt less firm for 300 miles.

My understanding is that the system does not like being pressure bled at more than 1 bar (14.5 psi) and that an ECU controlled valve will inhibit full bleeding above 14.5 psi. If it were me, I would get some more fluid (it's cheap enough) and methodically work my way around the 4 wheels and bleed again.
Click to expand...

Because I've bled the system with zero sign of any air i'm pretty sure my fault is with the master cylinder seals so have bought a new MC.
 
I bled the MC in situ you just have to remove the charge pipe and you get crack the two nipples with a 5mm ring spanner.

you can bleed the caliper for hours using 2 litres of fluid but if you don't bleed the MC the peddle will still travel to the floor and apparently flip the seals if you are not careful. I did introduce air as I just let the fluid drip out whilst I was servicing the calipers so the MC was empty, then the calipers do need to fill up a bit themselves before they can move anyway.
 
Stuart B said:
I bled the MC in situ you just have to remove the charge pipe and you get crack the two nipples with a 5mm ring spanner.

you can bleed the caliper for hours using 2 litres of fluid but if you don't bleed the MC the peddle will still travel to the floor and apparently flip the seals if you are not careful. I did introduce air as I just let the fluid drip out whilst I was servicing the calipers so the MC was empty, then the calipers do need to fill up a bit themselves before they can move anyway.
Click to expand...

What's the 'charge pipe'?
 
the bent pipe from the turbo outlet to the intercooler - its the bit in the way of reaching the MC bleed nipples. just two 13mm nuts and associated brackets and the Jubilee clips on either end to remove it. I think you can actually gravity bleed them too if you don't have an easy bleed kit. I didn't do anything to collect the fluid just let it squirt out, instead of correctly trying to collect it in a tube.
 
You don't want to do that, it will strip any painted surfaces it comes into contact with.
 
Stuart B said:
the bent pipe from the turbo outlet to the intercooler - its the bit in the way of reaching the MC bleed nipples. just two 13mm nuts and associated brackets and the Jubilee clips on either end to remove it. I think you can actually gravity bleed them too if you don't have an easy bleed kit. I didn't do anything to collect the fluid just let it squirt out, instead of correctly trying to collect it in a tube.
Click to expand...

If you let the brake fluid squirt straight out of the master cylinder bleed nipples how can you tell if the MC is bled correctly? At least with clear pipe you can see the bubbles.
 
I did say "...instead of correctly..." it bubbled out then flowed there is no paint nearby though, below is the drive shaft and floor, to the left is the heat shielding, right is the exhaust manifold in front is the down pipe. the space is pretty limited.
 
Stuart B said:
I did say "...instead of correctly..." it bubbled out then flowed there is no paint nearby though, below is the drive shaft and floor, to the left is the heat shielding, right is the exhaust manifold in front is the down pipe. the space is pretty limited.
Click to expand...

Fair enough! It sounds like the easiest method to bleed using the nipples whilst installed on the car.

Are bleed nipples on MCs a new thing I wonder? I mean all the bench bleeding info and general MC bleeding info I can find easily on the net refers to bleeding via the outlet pipes with not a bleed nipple in sight.
 
Update - I fitted a new master cylinder and bled using a pressure bleeder at < 1bar.

To do this I took all four wheels off and simultaneously bled the front then rear then the master cylinder. A few air bubbles came out here and there as you'd expect but nothing much and the fluid was soon flowing clear.

There was no change to my initial problem so I then went round and bled FL, FR, RL, RR then the master cylinder with the pressure bleeder and using some brake presses also. Still no change.

I drove the car and tested the brakes. Despite the brake pedal going to the floor if pressure is kept on my brakes work perfectly well. The ABS works too at each wheel. The weird thing is that once my brake pedal has gone to the floor there is more slack in my handbrake cable which suggests all that pressure is actually going somewhere.

It seems I've basically bled the fecker to death with not an air bubble in sight but based on the Audi workshop manuals all that remains to do is bleed the ABS. Unfortunately it turns out all my VAG-COM software will do is read fault codes and Ross-tech want hundreds of dollars for the software to bleed the ABS.

Is there any other way?
 
you also bled the system in the wrong order it should be RR, RL, FR, FL, MASTER 1, MASTER 2

are you sure your rear pads are auto adjusted to the discs? the fact the handbrake changes with the brake pedal pressed seems like pads are away from the discs unless your brake pedal is on the floor?
 
try pressing the brake pedal to see if the rear pads are even moving? no amount of bleeding will automatically adjust the caliper?
 
audi upgrades
Stuart B said:
try pressing the brake pedal to see if the rear pads are even moving? no amount of bleeding will automatically adjust the caliper?
Click to expand...
Yes, I bled the clutch.

Regarding the bleeding order I was following the Audi workshop manual here: http://workshop-manuals.com/audi/a3..._bleeding_appliance_vas_5234_or_v.a.g_1869_a/

I checked the brake operation but the rear pads are so close to the rotor that I couldn't see any movement when the pedal is pressed. They are working though as the handbrake stops the car and, when on slippery ground, I can feel the ABS kicking in at the rear. Also my rotors are nice and shiny.
 
  • Like
Reactions: Mav190sline
The car passed its MOT this week with an advisory that the offside rear brake was binding slightly.

Today I removed this caliper and took its piston out of the bore. The boot and O ring seal looked good as did the piston and the bore was OK. The oil that came out was a cloudy, dirty green mix of the blue fluid I put in a couple of years ago and the yellow fluid I put in recently. Clearly the bleeding had not flushed the bore out.

I gave everything a clean, copper greased the guide pins, wire brushed all the dirt and rust off the caliper, and replaced the pads and caliper, bled the brake and adjusted the handbrake. I also bled the master cylinder again but again no air in there.

The result of all this is no binding and my pedal's bite point is now further away. I guess this makes sense if everything is a little freer to move.

I can still push the pedal to the floor if I hold pressure on it though.

Could it be air in the ABS? Where does the pressure go when I hold my foot on the pedal?
 
As others will tell you you must bleed the master cylinder. There are 2 5mm nipples after removing the charge pipe.
 
Stuart B said:
As others will tell you you must bleed the master cylinder. There are 2 5mm nipples after removing the charge pipe.
Click to expand...

I did that - "I also bled the master cylinder again but again no air in there."!
 
I tried some more today.

First I tried bleeding the master cylinder whilst an assistant pumped the brakes. A few tiny bubbles were seen.

Next I attached a clear hose between each wheel's bleed valve and the master cylinder reservoir. I started with the fronts and finished at the rears. I pumped the brake at least 100 times per wheel until the fluid ran clear and totally bubble free.

The result was the pedal does feel a little more solid under braking but the pedal travel is still quite large, ie 50% of the total range, before the brakes are applied. If I press my foot on the pedal with the engine running it will just about go to the floor. The brakes stop the car perfectly well I must say.

I am basically in the same position I was before I replaced the master cylinder. Is this what the A3 brakes are supposed to be like? Argh.
 
I would be terrified if the brake pedal went all the way to the floor, that is not normal in any car.
 
I took the car to my local VAG / Audi specialist.

They hooked it up to a computer and gave it an ABS bleed. A few bubbles came out, they test drove it and reported all was well.

It has made no difference as far as I can tell and they can't explain why my pedal can be pushed to the floor only that a similar problem they never got to the bottom of was seen on a Golf Mk IV.

So annoying.
 
I have been in exactly the same position as you and done all that you have done including changing the Master Cylinder.... I wouldn't say ours goes all the way to the floor but it's certainly a much softer and longer traveling pedal than our A4,,, this all started about 7 years ago and has never been resolved and it's never failed an MOT so all can think is that that's how it is
 
the thing is - the thread was created after a brake pad changed - meaning it is something different to how the car used to be - so not sure why VAG would say it is normal - it hasn't been normal for 16 years.
 
had a simalar thing but on my C55, a small amount of air was being trapped in a pocket in the calipers and they needed to be taken off and bleed with the nipple at the top and a plate in the middle, this solved it
 
to be fair if it was me - I would probably take the calipers all off and apart to see if any dirty fluid is still in it - meaning the bleeding hasn't worked properly, or make the floor lower :D
 
  • Like
Reactions: hydro s3 and tcg
Red Ed said:
I took the car to my local VAG / Audi specialist.

They hooked it up to a computer and gave it an ABS bleed. A few bubbles came out, they test drove it and reported all was well.

It has made no difference as far as I can tell and they can't explain why my pedal can be pushed to the floor only that a similar problem they never got to the bottom of was seen on a Golf Mk IV.

So annoying.
Click to expand...
Ever found out what was causing the issue? Been dealing with this, did everything in the playbook with no success.
 
You must log in or register to reply here.

Similar threads

B
Brake pedal travel
Replies
9
Views
1K
Brad1011
B
B
Looooong brake pedal travel
Replies
16
Views
2K
btmotorsport
B
<tuffty/>
Long brake pedal travel
Replies
19
Views
18K
5teve L
5
R
Long travel on brake pedal after bleeding.. Help!
Replies
12
Views
11K
Rice
R
sparkysi90
Brake pedal problem
Replies
10
Views
833
Slammedorion
Slammedorion
Top
Back