HELP!!! --- 04 A4 Avant - brake problems - soft pedal

[Joesturbo]

Hi,
I am having a problem with my brakes where I feel like the pedal is going to the floor... I replaced the rear with new pads and disks - worked like a champ. Then recently I had the front rotors turned and new pads put on unfortunately, since that time the brakes have been essentially "working" but the pedal travel goes to the floor when braking hard.

It has been a couple of weeks and the machining of the front rotors has not even been polished yet and they are not smooth on either side. I had the entire system flushed this morning and no real improvement at all.

Is there a vagcom procedure for brakes that needs to be done?

Thank in advance for the helP!!!!

[moyenecorniche]

Hi,
I am having a problem with my brakes where I feel like the pedal is going to the floor... I replaced the rear with new pads and disks - worked like a champ. Then recently I had the front rotors turned and new pads put on unfortunately, since that time the brakes have been essentially "working" but the pedal travel goes to the floor when braking hard.

It has been a couple of weeks and the machining of the front rotors has not even been polished yet and they are not smooth on either side. I had the entire system flushed this morning and no real improvement at all.

Is there a vagcom procedure for brakes that needs to be done?

Thank in advance for the helP!!!!

There is but on an Audi you should not have your rotors turned, they need to be replaced period.
Pedal travel sounds like you still have air somewhere in the system.

Who did you have work on your brakes...? I hope they were Audi certified mechanic/tech. Doesn't sound like it...
i suspect that whoever did your front brakes may have undone the brake lines and allowed air to contaminate the system and never bothered to purge the air out after reinstall of your rotors which should not be done in the first place, if they need turning then they need to be discarded and replaced, especially in a 7+ year old car. Just the problems you are having means you should find elsewhere to have your B6 worked on.
This isn't a Vagcom problem as it is mechanical and not related to ABS or ESP system, those should not have been affected or played with.
Rotors, pads, lines, calipers are fairly simple to replace but purging the system is time consuming as it often has to be done repeatedly after a brake component replacements..

BTW...Have your lines been checked for leakage, they also may need replacement, i would have your system checked thoroughly by a reputable VAG shop..

Go to A4 mods, there should be some tech you can use, also got to the A-zine tech section and look up brakes and suspension, there are multiple threads dealing with the B6 A4 brake system and DIY's trouble-shooting.

http://www.a4mods.com/index.php

[Joesturbo]

There is but on an Audi you should not have your rotors turned, they need to be replaced period.
Pedal travel sounds like you still have air somewhere in the system.

thank you for your other tips will look into the A4mods site...

I do disagree with you on turning the rotors - turning rotors once
should not matter... audi turned my rears under warranty and put on new pads...

I will keep digging

[imnuts]

thank you for your other tips will look into the A4mods site...

I do disagree with you on turning the rotors - turning rotors once
should not matter... audi turned my rears under warranty and put on new pads...

I will keep digging

I have not heard of anyone ever having a dealer turn rotors on the B6. I've read of people having independent shops do it, but never a dealership. I've also never heard any recommending that it be done on a B6, and it has always been said that they should be replaced. If you don't machine them properly, you're going to alter the hardness of the rotor, killing its life faster, and potentially impacting performance.

[B5Burn]

We don't even have the lathe in our dealership.

Rotors are less than $60 each, require replacing as they wear as much as the pads. Unlike cars back in the day with asbestos pads.

Air in your system or maybe the caliper pistons are ratcheted too far to allow for a toight pedal?




B.

[B5Burn]

Ps, who did do the machining? I hope you trust them as your pads are new.. Would suck if they wear unevenly, due to the machinist not performing the job correctly.

In rereading your post, the fact your pads haven't bedded into those front rotors makes me think you're being stopped by the rears only (mostly). That's bad. Your front brakes are where most of your stopping performance is required and done.


B.

[Charles.waite]

I would have a reputable shop re.bleed the brakes. Clearly air was introduced into the system somewhere. Maybe the shop took the shitty route and opened the bleeder valves when backing the caliper pistons and forgot to close them right away and got air in the system.

In any event i doubt it has anything to do with the machining of the rotors (I disagree with you all btw, but that's a whole 'nother discussion). Get the brakes re.bled or better yet fully flushed with new fluid and I bet the problem will be solved, provided the shop knows how to properly bleed the brakes. Hint: the normal mashing the pedal method doesn't work very well, power bleeders are much preferred and are somewhat idiot proof.

[B5Burn]

What was your rotor thickness when the pads were replaced?




B.

[Joesturbo]

I had my local guy who I fully trust work on the car -on Saturday I had them do an overall system flush using a power bleeder. So all new fluid is in the lines now and there should not be any air. I need to measure the thickness of the rotors, but being that these cars are rear bias and that the fact that this was the second set of pads - I can't imagine there is a problem with the rotors being too thin. Does anyone know what the thickness should be? and what the tolerance is?

thanks again everyone -if no clear ideas are out there - I am going to just replace them with new rotors.

[B5Burn]

I had my local guy who I fully trust work on the car -on Saturday I had them do an overall system flush using a power bleeder. So all new fluid is in the lines now and there should not be any air. I need to measure the thickness of the rotors, but being that these cars are rear bias and that the fact that this was the second set of pads - I can't imagine there is a problem with the rotors being too thin. Does anyone know what the thickness should be? and what the tolerance is?

thanks again everyone -if no clear ideas are out there - I am going to just replace them with new rotors.

Having reported that, seems logical. MAYBE a line is leaking somewhere? If your car is fairly clean run your hands over the soft lines behind the wheels... Real shot in the dark on that one. See if anything is dribbling..




B.

[lov2fly]

Audi’s are front bias; your VW is rear bias.

The rotor thickness tolerance is stamped into the rotor hub. My personal experience is not to cut or turn rotors on European cars, since the tolerance is minimal. My rule of thumb is 2 sets of pads for one set of rotors. If the rotors are not smooth enough or have too much of a lip, they are too thin to cut and have to be replaced. Rotors being too thin would cause the rotors to overheat, causing wobbling of the rotors, pulsing in brake pedal and shaking in the steering wheel.

A VagCom procedure for brakes needs only to be done, if you got air in your ABS pump (very unlikely by just changing pads).

Reading your post, the fact that your fronts haven't bedded in, makes me think you're being stopped by the rears, mostly. Hence, the pedal travel goes to the floor when braking hard.

[Joesturbo]

I am thinking that too -the ABS comes on when I stop hard... maybe there is air in the ABS pump some how? I don't know how they bleed the brakes when they put them on... I am going to connect my VAGcom tomorrow after work and go through the process. Anyone have the steps>? Doing the research now.. will add if I find.

thanks everyone
Joe

[B5Burn]

Worth a look for sure, my technicians tell me it's uuuusually only required if the module has been disassembled (dried out). But check it out.




B.

[Charles.waite]

Audi’s are front bias; your VW is rear bias.

no to be super picky but I'm pretty sure our b6 stock brakes are rear biased. Hence why the rear wheels always get dirtier much after than the fronts. My b7 is more front biased, as the front wheels getr way dirtier than the rears. Our b6s are super special like that, and it's part if the reason our brakes suck balls.

[drjonez]

I am thinking that too -the ABS comes on when I stop hard... maybe there is air in the ABS pump some how? I don't know how they bleed the brakes when they put them on... I am going to connect my VAGcom tomorrow after work and go through the process. Anyone have the steps>? Doing the research now.. will add if I find.

thanks everyone
Joe

It has been my experience that it takes drive time to get all the air out of the system. You can bleed all you want....but get some drive time in and the trapped air comes out, then rebleed to remove it.

[lov2fly]

no to be super picky but I'm pretty sure our b6 stock brakes are rear biased. Hence why the rear wheels always get dirtier much after than the fronts. My b7 is more front biased, as the front wheels getr way dirtier than the rears. Our b6s are super special like that, and it's part if the reason our brakes suck balls.

VW is rear bias - Yes this is incorrect

B6 A4 1.8T bias is:
68.1% front
31.9% rear
2.1 F/R

Auto manufacturers like our cars to be front-biased in all conditions achievable. This helps to insure vehicle stability under braking by the mass public.

[Joesturbo]

OK - making some progress here... did some more checks on recomendations AND my main technician at my Audi dealer suggested several hard (both feet on the pedal) ABS stops. Once I did a couple I started to feel the front brakes start to work and checked the rotors. Indeed the pads are starting to bed - I still don't understand why these pads would have the effect they have had - but non-the less - sometimes mechanical items can cause unique problems that are not apparent... will be keeping an eye on it for a while though.

thanks everyone for your tips...

[imnuts]

no to be super picky but I'm pretty sure our b6 stock brakes are rear biased. Hence why the rear wheels always get dirtier much after than the fronts. My b7 is more front biased, as the front wheels getr way dirtier than the rears. Our b6s are super special like that, and it's part if the reason our brakes suck balls.

Which wheels get dirty isn't a good scale of which brakes are working more. Differences in air flow over the wheels/brakes, what you drive through, pad type, and tons of other factors would determine this. My back window is always dirtier than the front, doesn't mean it gets used more.