Panic assist brake removal

[nihil]

Long story short, they've been bothering me off and on for a while now, and after locking up again today, it was the final straw. Someone, somehow has to know how to get rid of this nuisance. Anyone out there with diagrams, knowledge, or previous experience?

[a2gtinut]

there is something wrong with your car.

[nihil]

there is something wrong with your car.

Yes, it's called panic assist braking. Do you know how to get rid of it?

[heateris]

Yes, it's called panic assist braking. Do you know how to get rid of it?

was it an option? i've never heard of it.

[B6Lovin]

maybe you need to stop slamming on your brakes. no offense or anything, but you seem to keep getting in situations where the car feels the need to do this...

i drive my car, VERY HARD.. and i have never ONCE had this happen.. guess i just dont see why this keeps happening. either you need to fix your driving - or like someone said earlier, something on your car is broken.

[nihil]

was it an option? i've never heard of it.

It's a disgruntled engineers idea of a sick joke if you ask me.

Actually it was intended to be a "safety feature", but it was poorly executed in my opinion. When you step on the brakes hard and quickly (both pressure and response time factor into it), the pedal sticks to the floor, preventing you from moving anywhere for 5-10 seconds. Supposedly the mechanism behind this is giving you more braking ability than normal, but with ABS already in place, I don't see that being very plausible.

I've been trying to get the Bentley/eBahn manual working so I can look up brake controller coding, but it's a piece of shit and wont register properly, and Bentley support is about as worthless as tits on a tomcat.

If you'd like to see them in action for yourself, find an empty parking lot or other appropriate surface (asphalt, tarmac, concrete, etc..), bring it up to 30-35mph, then slam on the brakes hard and fast. If done hard and fast enough, the pedal will bottom out and stick there for about 5 or 10 seconds (feels more like an hour when you're in the middle of an intersection).

I've had it happen 3 times on public roads now (previous thread), and I'm sick of it, when I take my foot off the brake pedal, I expect the brakes to let go right then and there. If I can't find a way to disable it, and I hate to say this, but getting rid of the car looks like the way it'll go.

[B6Lovin]

im dead serious man, that shouldn't happen as often as it does to you -- check to see if something is broken...

[nihil]

maybe you need to stop slamming on your brakes. no offense or anything, but you seem to keep getting in situations where the car feels the need to do this...

i drive my car, VERY HARD.. and i have never ONCE had this happen.. guess i just dont see why this keeps happening. either you need to fix your driving - or like someone said earlier, something on your car is broken.

If you've never had it happen, you aren't driving it as hard as you think. I was driving only mildly spirited on a back road today on the way to a museum, not even close to balls out, even for the lethargic A4.

And yes, there is something on my car that is broken, the presence of panic assist braking. I'd like to remove that subsystem, do you have input regarding the process?

[nihil]

im dead serious man, that shouldn't happen as often as it does to you -- check to see if something is broken...

Rotors < 5k, pads < 5k, fluid clean/full, no codes from brake controller, tires equally inflated to 32psi, tires in excellent condition. Any other ideas?

[B6Lovin]

If you've never had it happen, you aren't driving it as hard as you think. I was driving only mildly spirited on a back road today on the way to a museum, not even close to balls out, even for the lethargic A4.

And yes, there is something on my car that is broken, the presence of panic assist braking. I'd like to remove that subsystem, do you have input regarding the process?

you have no idea.... i've driven my car in a manner that 99% of the people here would probably frown upon lol. balls out is my middle name when i hit the twisties - and my a4 is anything but lethargic. (even when my car was stock i made fools of people driving much faster and more powerful cars..)

the point is that i've been in all types of situations (driving hard, getting cut off, not paying attention to traffic, deer, dogs, etc) where i was really working my brakes - some harder than others, some faster than others - and some as fast and hard as i've ever hit the brakes on any motorized vehicle... and i've never had this issue. a lot of people on here have hit their brakes plenty hard and not had this happen... even coming to a complete and full stop - my pedal doesn't "stick" to the floor.

what I'm getting at is that maybe you should have that function and the things which factor into when it activates checked out... nobody seems to have this issue but you - especially not 3 times all close together. so quit saying the function is the issue and find out for sure whether yours is working the way it should or not.

THEN, depending on what you find - you can sit down and figure out whether its the way you're driving/hitting your brakes, or if it was just something broken. and you can be happy with your a4 like the rest of us lol.

<tone = CHECK IT FIRST, but not argumentative or mean>

[B6Lovin]

Rotors < 5k, pads < 5k, fluid clean/full, no codes from brake controller, tires equally inflated to 32psi, tires in excellent condition. Any other ideas?

a bad ABS module or something of the sort. an overly sensitive sensor or w/e controls it. maybe find someone else with an a4 and see if their car reacts the same way under the same circumstances. maybe you can post a video of exactly how much braking force its taking you to make this happen?

i really do want to help you, i'd hate to see you get rid of your a4 over something like this when i KNOW that it's not normal... i've sent clouds of smoke curling from all 4 tires when hitting my brakes and then just driven off like normal with no "stick" afterwards

[brewmastr]

the feature is called BAS, Brake assist system, the booster uses a dual diaphragm design, and when you brake suddenly a stroke sensor on the booster detects this and provides added vacuum assist from the 2nd diaphragm in the system, this design is EXCELLENT, and your piss poor reasoning of this being crap just tells me you dont understand the system whatsoever. your pedal should not stick to the floor or drop to the floor, when the 2nd diaphragm kicks in you will feel a pedal drop but nothing that significant and yes it may initiate a ABS stop but that is only if you are really slamming that brake pedal down to the floor and asking for the abs stop. you may have something wrong with the booster or some air in the system causing it to act funny, when was the last time you flushed your brake fluid to get all the air and old fluid out?

[brewmastr]

and if you want to remove it, unplug the stroke sensor at the booster and put in a resistor of the same value. but seriously something is wrong with the system. If you would like some real documentation on the system i can scan some stuff and send it to you so you can educate yourself, the brakes at no point should hold and apply themselves, its a simple vacuum assist as soon as you let off the pedal it should come back up to you, you have something broken, and considering its on a vital saftey system, i would advise getting it fixed asap. our brakes our purely mechanical, the abs pump valves just dump and hold they do not apply pressure,so as soon as your off the pedal that pressure is off and the brakes should not stay applied so it seems like your booster or master cylinder is causing something to stick up. as far as getting a car without it, my god this feature is on almost everything now, people dont even know they have it by the response of the a4 forum, but its pretty standard now a days especially on german cars, benz has been using this since the early 90's, i checked out the previous post, and old guy as genious as he normally is, is showing he is human the system does not work as he described, i will gather up my training information on it from mercedes benz, its the same exact system and scan it and post it here tomorrow, so you guys know how the system works and under which conditions it will initiate a stop, yes the pedal will drop but it should not ever "stick" that is a huge saftey concern itself, the 2nd diaphragm just instantly puts you to maximum full vacuum assist stop, the idea behind this is that most people when braking in a sudden panic stop do not apply the brakes as hard as they can and by providing full assist right away this provides much greater stopping distances.

[B6Lovin]

^THANK YOU


told you something wasn't right.

[Jet Jockey]

Long story short, they've been bothering me off and on for a while now, and after locking up again today, it was the final straw. Someone, somehow has to know how to get rid of this nuisance. Anyone out there with diagrams, knowledge, or previous experience?

I'm sorry I never got around to your PM on this matter, just too busy these days. I agree with you it's a crappy system. I am now liberated from it and the whole ABS system and I am so happy. Even tracking the car is better without ABS.

Now after reading the thread I feel that perhaps there is something wrong with the car. Did you ask an Audi tech to test drive it with you?

In any case If this situation repeats itself often and didn't in the past maybe there is something wrong with the braking system. The bad news is I don't think the panic assist (lol) can be removed because I think it's a function of the ABS controller (its program) or the way the booster works (two stage).

A few years back I complained to my dealer that I felt the front brakes were too sensitive and would lock up prematurely. I went on a test drive with a tech with their fancy computer and everything was within specs.

They went on to say that perhaps my BBK was the culprit and did not want to venture any further. So I waited until the next fall (this was summer time) when I reinstall my OEM brakes for winter use and when I got the same symptoms I took it back in and showed them. Finally they would believe me and could not blame the BBK so they ended up changing the ABS pump/controller IIRC.

[nihil]

you have no idea.... i've driven my car in a manner that 99% of the people here would probably frown upon lol. balls out is my middle name when i hit the twisties - and my a4 is anything but lethargic. (even when my car was stock i made fools of people driving much faster and more powerful cars..)

the point is that i've been in all types of situations (driving hard, getting cut off, not paying attention to traffic, deer, dogs, etc) where i was really working my brakes - some harder than others, some faster than others - and some as fast and hard as i've ever hit the brakes on any motorized vehicle... and i've never had this issue. a lot of people on here have hit their brakes plenty hard and not had this happen... even coming to a complete and full stop - my pedal doesn't "stick" to the floor.

I'm sure you've got tons of experience, and are the fastest around, and have pushed your car to its utmost limits. Given all this, I find it odd you haven't encountered this safety device.

what I'm getting at is that maybe you should have that function and the things which factor into when it activates checked out... nobody seems to have this issue but you - especially not 3 times all close together. so quit saying the function is the issue and find out for sure whether yours is working the way it should or not.

The rest of the braking system checks out 100%. The panic assist kicks in when you stomp on it (when I would expect ABS to kick in). It only does it on dry asphalt (so far), ABS kicks in on the gritty/slippery stuff long before panic assist does (I've yet to trigger PA in slippery conditions).

THEN, depending on what you find - you can sit down and figure out whether its the way you're driving/hitting your brakes, or if it was just something broken. and you can be happy with your a4 like the rest of us lol.

What I've found is that it's behaving in a manner inconsistent with how I expect a car to behave, and that all systems appear fully functional. I will be happy with the car once it's gone (and after a few more upgrades).

a bad ABS module or something of the sort. an overly sensitive sensor or w/e controls it. maybe find someone else with an a4 and see if their car reacts the same way under the same circumstances. maybe you can post a video of exactly how much braking force its taking you to make this happen?

Bad ABS module/sensor would throw codes. I have none. As for taking a video of the event, that would be effectively useless in determining braking force. I do however have some accelerometers around here somewhere

i really do want to help you, i'd hate to see you get rid of your a4 over something like this when i KNOW that it's not normal... i've sent clouds of smoke curling from all 4 tires when hitting my brakes and then just driven off like normal with no "stick" afterwards

Based on what I've been reading, that's not "normal" for these cars. ABS should prevent them from locking up, which would prevent them from smoking. ABS should logically kick in before the panic assist, unless conditions are sticky enough for the tires to grip like stink on shit. Either way, you shouldn't have a means of smoking your tires on braking unless you've modified your brake system.

[brewmastr]

jet being that your car is a track monkey of course it is better without the system lol.

[Jet Jockey]

jet being that your car is a track monkey of course it is better without the system lol.

What I really like about the new set up is that you the driver is the one controlling the brakes and not some vacuum system or some electronics.

You have a direct link and a direct input to the calipers via leg power and you do have to push hard but the results are amazing... total control.

[brewmastr]

is the system you set up not power assist?

[brewmastr]

oh i have never tried this with our cars but have with benz, so it may be a possibility through vag-com, but you should be able to activate BAS at idle with scan tool, that way you can see whats happening without having to drive it and activate it via a hard stop, this may be helpful in determining what is causing the pedal to stick.

[B6Lovin]

I'm sure you've got tons of experience, and are the fastest around, and have pushed your car to its utmost limits. Given all this, I find it odd you haven't encountered this safety device.

i'll ignore the sarcasm. my point was that i've pushed the hell out of my car and never had this happen - neither has anyone else (if they have they haven't come forward)

The rest of the braking system checks out 100%. The panic assist kicks in when you stomp on it (when I would expect ABS to kick in). It only does it on dry asphalt (so far), ABS kicks in on the gritty/slippery stuff long before panic assist does (I've yet to trigger PA in slippery conditions).

What I've found is that it's behaving in a manner inconsistent with how I expect a car to behave, and that all systems appear fully functional. I will be happy with the car once it's gone (and after a few more upgrades).

Bad ABS module/sensor would throw codes. I have none. As for taking a video of the event, that would be effectively useless in determining braking force. I do however have some accelerometers around here somewhere

i take it you've had it in to a few shops to check things out right? (im too lazy to go back through the other threads, i do remember seeing them and briefly glancing through them though) if not maybe shop around and see if someone else can find something the first guy missed. I know that seems obvious but it's worth doing at this point.

i realized how dumb the video thing sounded after i said it lol - but i figured you would get the idea. if you have fancy tools (or even a g-tec pro) and can get an idea of how much braking force it takes to make your pedal stick - i'll make time to go do some 60-0 runs once my car is back up and running. (all i have at my disposal is a friend's g-tec pro lol)

Based on what I've been reading, that's not "normal" for these cars. ABS should prevent them from locking up, which would prevent them from smoking. ABS should logically kick in before the panic assist, unless conditions are sticky enough for the tires to grip like stink on shit. Either way, you shouldn't have a means of smoking your tires on braking unless you've modified your brake system.

ABS prevents lock up in theory -- but you've only got as much stop as your tires. no matter how fast or hard ABS may try to pump the brakes, a skid is not impossible on dry pavement - especially with shitty 215 pilot HX's... trust me. and my brakes are 100% stock aside from hawk pads. (to the dismay of some hahaha, i think stockers do just fine for my purposes - im considering b6 s4 at the most for a little extra bling.. or MAYBE a BBK that'll shave some weight)

[nihil]

the feature is called BAS, Brake assist system, the booster uses a dual diaphragm design, and when you brake suddenly a stroke sensor on the booster detects this and provides added vacuum assist from the 2nd diaphragm in the system, this design is EXCELLENT, and your piss poor reasoning of this being crap just tells me you dont understand the system whatsoever.

Unfortunately I do not understand it nearly as well as I'd like, getting docs has proven a bit elusive. But with the understanding that this is "normal" behavior, it would indeed give me the opinion that it is crap.

your pedal should not stick to the floor or drop to the floor, when the 2nd diaphragm kicks in you will feel a pedal drop but nothing that significant and yes it may initiate a ABS stop but that is only if you are really slamming that brake pedal down to the floor and asking for the abs stop. you may have something wrong with the booster or some air in the system causing it to act funny, when was the last time you flushed your brake fluid to get all the air and old fluid out?

Have not flushed it, fluid is clear, clean, full, and has not changed level in the ~6 months I've owned it. It's on the to-do list, but hardly seems relevant to the issue at hand.

and if you want to remove it, unplug the stroke sensor at the booster and put in a resistor of the same value.

Now here's a mod I can sink my teeth into

but seriously something is wrong with the system. If you would like some real documentation on the system i can scan some stuff and send it to you so you can educate yourself

I would -love- documentation, the more the better. I'm a total information whore, just had a shit run trying to get this Bentley manual working, and there doesn't seem to be a paper version.

the brakes at no point should hold and apply themselves, its a simple vacuum assist as soon as you let off the pedal it should come back up to you

I couldn't agree more.

you have something broken, and considering its on a vital saftey system, i would advise getting it fixed asap. our brakes our purely mechanical, the abs pump valves just dump and hold they do not apply pressure,so as soon as your off the pedal that pressure is off and the brakes should not stay applied so it seems like your booster or master cylinder is causing something to stick up. as far as getting a car without it, my god this feature is on almost everything now, people dont even know they have it by the response of the a4 forum, but its pretty standard now a days especially on german cars, benz has been using this since the early 90's, i checked out the previous post, and old guy as genious as he normally is, is showing he is human the system does not work as he described,

I do pay a bit more attention to his posts than many others, hence my thinking that the behavior was normal. And though I'm happy to learn that the car I've grown to love really isn't an intolerable twat, I'm now concerned that something isn't right.

i will gather up my training information on it from mercedes benz, its the same exact system and scan it and post it here tomorrow, so you guys know how the system works and under which conditions it will initiate a stop,

I'd really appreciate that, and I'm sure others would too.

yes the pedal will drop but it should not ever "stick" that is a huge saftey concern itself, the 2nd diaphragm just instantly puts you to maximum full vacuum assist stop, the idea behind this is that most people when braking in a sudden panic stop do not apply the brakes as hard as they can and by providing full assist right away this provides much shorter stopping distances.

We're car enthusiasts, not most people, so the mod may be useful to offer a most consistent pedal. I'm a decent sized guy (6'2"/200lbs) and when I stick my foot in something I'm not shy at all about it. The brakes in the A4 feel linear up until they hit that panic point where they lock up. If I can get a fully linear pedal out of the mod without losing any potential braking force and not losing ABS, I'll go that route.

I'm not saying I won't address the bottom out and stay there issue, that will be the first thing. But I'd prefer something fully linear and smooth over something thats nice up until it freaks out and tries to kill you, that's like dating an Italian woman.

[absolutegtr]

I am with B6lovin on this on,I have never encountered this before with my car. Its a wierd "ritual" I go through, lol, but about once a month I make a habit of it to completely slam on the brakes many times in row (to ensure the ABS is still working and all). Wierd I know, but i have not once had this problem.

but i do know what you feeling, because it has happened to me once before in my moms expedition. Someone had cut me off,and I hit the brakes just enough to slow the car down, but for some odd reason, the pedal decided to apply full force upon it self, and it literally felt like the pedal dropped to the floor. So I decided to do some research and found out that on all newer cars that are equipped with the panic assist system, will draw more vacuum from the engine and will, in a sense, apply the brakes for you...which is that feeling you are getting of the calipers sticking after you release the brake pedal. Anyways, this information I gathered also said, that it was made for like a old person, who maybe cant apply full force on the pedal, it will "assist" in pushing the pedal for you. I believe that if you "slam" on the brakes and dont apply (what the computer) would see as "full force", it will "assist" in pushing it down for you....

I hope that makes sense, i am trying to recall info from like a few months back, and am typing after a crazy night....can barely see the keyboard, lol

[nihil]

I'm sorry I never got around to your PM on this matter, just too busy these days. I agree with you it's a crappy system. I am now liberated from it and the whole ABS system and I am so happy. Even tracking the car is better without ABS.

Your brake system amazes me, as does the rest of your car. One day I hope to have the balls to do that to mine. No biggie on the PM, with the way shit is flying out of your car, I figured you weren't even looking at 75% of it anyway

Now after reading the thread I feel that perhaps there is something wrong with the car. Did you ask an Audi tech to test drive it with you?

Bah, I only go to the dealership for small parts, and paid mechanics are for doing things like mounting tires and alignments (things I don't have equipment for). I'm one of those "I do my own work" types, grew up working on things mechanical, and it never made sense to pay others to do it for me.

In any case If this situation repeats itself often and didn't in the past maybe there is something wrong with the braking system. The bad news is I don't think the panic assist (lol) can be removed because I think it's a function of the ABS controller (its program) or the way the booster works (two stage).

I was thinking that the values for triggering the response could be changed in the controller, but the resistor mod looks good too.

A few years back I complained to my dealer that I felt the front brakes were too sensitive and would lock up prematurely. I went on a test drive with a tech with their fancy computer and everything was within specs.

They went on to say that perhaps my BBK was the culprit and did not want to venture any further. So I waited until the next fall (this was summer time) when I reinstall my OEM brakes for winter use and when I got the same symptoms I took it back in and showed them. Finally they would believe me and could not blame the BBK so they ended up changing the ABS pump/controller IIRC.

Did your pedal ever stick to the floor?

[old guy]

I agree completely that nihil’s BAS (AKA panic assist) is not functioning properly. In his original posting I made the erroneous assumption that it was probably his first encounter with the BAS and I know that it can be rather disconcerting when your brake pedal seems to temporarily have a mind of its own. However, the system was obviously not designed to be that intrusive as to incapacitate the car. My advice would be to get the braking system functioning properly and then decide if the panic assist is really an issue.

Oh and by the way brewmastr, it’s spelled genius.

[nihil]

Any ideas where to start diagnosing this one? The brakes behave normally on all surfaces, unless you hit them hard on a dry grippy surface and this panic assist kicks in, then it bottoms out (as seems to be expected), then stays there for several seconds (seems to be broken). I'm going to split this up into two separate issues, BAS/PA kicking in sooner than it should (rather, not when I expect it), and pedal not releasing itself from the floor.

For the first issue, kicking in sooner than I expect, I'm sure that's all driving style. In hard/emergency braking situations I get on them quick and hard right up to the point where I expect them to lose traction (if they were linear in response), then modulate the pedal from there. I'm guessing the computer is seeing this as "he's in a rush to stop, but not slamming on the brakes as hard as he could", and is giving me that extra stop whether I want it or not. I don't, I'd much prefer a linear/predictable pedal.

Second issue, and the one that bothers me the most, is the pedal sticking to the floor when BAS kicks in. Since it only seems to do it when BAS is activated, and the rest of the braking system appears in good shape, it seems reasonable that we can eliminate unrelated bits of hardware, leaving us with (and I'm pulling this out of thin air, as I've still not seen docs):
- brake pedal sensor
- brake controller module (though I question this one as it shows no codes and otherwise operates without issue)
- solenoid/valve somewhere in the system that would keep pressure from being relieved
- 2nd diaphragm in the booster has a hole in it perhaps?

Any other ideas?

[Redgoat]

I wasnt aware our cars had this.. I have never encountered it. I was at the track last in May and did some brake testing.. get up to about 60 and SLAM the brake as hard as possible.. did it many times to the fact where my brake fluid was boiling.. never had the pedal stick though. Was this only in some model years?

[nihil]

I wasnt aware our cars had this.. I have never encountered it. I was at the track last in May and did some brake testing.. get up to about 60 and SLAM the brake as hard as possible.. did it many times to the fact where my brake fluid was boiling.. never had the pedal stick though. Was this only in some model years?

If what I've been reading is correct, it's standard on all our cars. The sticking part seems to only be standard on my car.

[brewmastr]

well i just got home from work so havnt had a chance to scan that stuff yet but just wanted to get on here and give my opinion of what your looking at your problem being after looking through my training info on BAS, ok first of all break down of the system is you have inputs (sensors) that talk to esp control module, and then esp control module activates BAS, so here is how it works, your inputs to the ESP are the pedal stroke sensor, diaphragm movement sensor (inside the booster, not replacable), brake light switch, circuit 30 (batt +) circuit 15 (switched power) and circuit 31 (ground), those items input to ESP control module and the module then determines if condtions are appropriate to activate BAS, when it activates BAS it activates a solenoid that is called a diaphragm release valve, and it releases the vacuum in the pedal diaphragm to the diaphragm that is pushing against the master cylinder giving you the added vacuum boost. now given the way the system works we can cancel out the ABS pump being a culprit, you had stated earlier your abs operation is ok when you are in a abs stop without BAS active, the way it sounds to me is that you have a booster issue, the pedal stroke sensor is acting properly, and it seems like esp control modue is activating BAS at the correct time, but the problem with the pedal sticking seems like something is binding up in that brake booster when it releases that diaphragm, that and the dramatic sink in your pedal, im going to go out here in a bit after i get some dinner in me and see what you need to do to activate bas while stopped and in idle via vag-com, it shouldnt be a pedal drop to the floor but more like maybe an inch or so, and it should not feel as it is not linear, it should be smooth as that release valve should open up near instantly as soon as it sees the pedal stroke sensor traveling at a high rate of speed, hence why almost no one knows there cars have this technology, yes this technology is on all b6 a4s and alot of cars, domestics, japenese imports, and ALL the german cars use this now. it is good technology, but this is just an example of when good technology goes wrong how it can potentially be a big problem.

oh and to old guy, is this a frikin spelling bee haha, thats exactly why you are the genius.

[brewmastr]

well after communicating with the abs/esp control module on our cars with the vag-com i cannot get an activation for BAS, it just cycles through each wheel activating the pump for each wheel. so i guess there is a limitation right there with vag-com.

[nihil]

I just spent a few minutes in a large parking lot flogging the brake pedal. Some things I noticed:

- Does not lurch to either side when it sticks.
- No predictable time before pedal restores, in fact there was about 30-45 seconds after one particularly hard stop it didn't come back, and I got real worried.
- ^Was remedied by tapping repeatedly on the pedal (that's what I was doing when it came back at any rate).
- ^Repeatable, though comes back faster if I don't slam them as hard.
- It definitely seems to only happen when BAS kicks in, it's not linear at all.
- The rear cup holders are a lot more useful than they appear.


I'm going to disable BAS, just for the sake of a linear/predictable pedal if nothing else, but I'm hoping it will also serve as a buffer to the locking up issue until I can figure out what is causing it.

All of your input is appreciated. I'm going to try, yet again, to get this broke ass Bentley manual working so at least I have some idea of what the system looks like without having to tear the thing apart.

[JMRQuattro]

I think it's weird that you're slamming on the brakes enough to feel this as often as you say. Under what circumstances during regular daily driving should you ever need to be slamming on the brakes this often unless you're constantly getting into accident situations? Or having small children or animals run out in front of you? It just doesn't make sense. My brake pedal is never anywhere near the floor. Unless you come to a skidding hault at every stop sign and stop light, or delay your braking to the utmost final second before entering a turn, this should not be happening. Unless like everyone else is saying... it's overly sensitive. And as far as sticking to the floor? Of the times i've been driving at around 40 or 45 mph and slammed on my brakes as hard as humanly possible and kept my foot pressed, the most i've ever encountered is what feels like a hiccup from the brake pedal. A pulsing which i'm sure is just the ABS doing it's job. but once i release from the floor, the pedal comes back up with me. So it sounds like you might have a combo of both way too hard of braking on a regular basis, and a broken system. I feel bad for your passengers if you ever have them. Whenever i'm in the car with someone who brakes hard i'm scared to death and i want to just knock the driver out and take over because i feel like i'm going to slam into the car in front of us. Pushing my right foot hard against the floor of the passenger seat desperately wishing it were a brake is not a comfortable feeling. Your passengers probably hate you.

[nihil]

Well, after some digging around, it looks like AoA will cover damages caused by water build up due to the plenum clogging recall, which my car happens to be covered by. If this problem is with the booster, and was caused by said issue, it looks like I'll be able to coast this one on Audis tab. Though it would drive me absolutely nuts letting someone else work on one of my vehicles.

At any rate, it'd save me some scratch I can put towards wheel bearings.

Going to give AoA a call tomorrow and see what the deal is.


On a side note I pulled the bottom part of the driver side dash off today to check out the pedal travel sensor. The more I take off of this car the more I'm amazed at how well engineered most of it is (still pissed at the brakes). They definitely considered their techs when they designed it.

[brewmastr]

pedal travel sensor is located on the outside of the booster, you are probably looking at the brake light switch, anyhow, i totally forgot about the plenum recall and that is exactly what the recall was inititated for i belive, water gets into the booster and i think there concern was with it freezing causing sticking pedal, but if shit is rusted up in there it will do the same thing, good catch man, make audi put a new booster in it. i would do that before you go disabling any systems in the car, BAS does work remarkably well when it operates correctly.

[nihil]

pedal travel sensor is located on the outside of the booster, you are probably looking at the brake light switch

Are you sure? I took a quick look around the booster and didn't see anything obvious, so I popped the panel off and took a few pictures. The brake pedal switch/sensor has 4 wires, and is engaged through full pedal travel, where the other similar switches have only 2 wires, and are momentary contact. I didn't take a meter to it (handheld scope is in the mail ), but my guess was that two of those wires were momentary contact switched, with the other two potentiometer style resistance, serving brake lights and BAS respectively.

anyhow, i totally forgot about the plenum recall and that is exactly what the recall was inititated for i belive, water gets into the booster and i think there concern was with it freezing causing sticking pedal, but if shit is rusted up in there it will do the same thing, good catch man, make audi put a new booster in it. i would do that before you go disabling any systems in the car, BAS does work remarkably well when it operates correctly.

Thanks, and I'll give the BAS a shot once everything is sorted out, but I'm still a bit skeptical. From the sounds of it, BAS would toss the proverbial monkey wrench into what has become an instinctive reaction for me, and I'm not sure I want to change my driving style to suit that, as I do have other vehicles without the fancy gadgetry.

[nihil]

Dropped the car off at the dealer this morning and have been putzing around in a B7 today. Just got a call from them, and it is in fact the brake booster, and they are covering it under the recall. The bad news is they wont have the part until Wednesday, and want to keep me in a loaner until it's done.

[brewmastr]

glad we were able to help you in diagnosing this problem, i cant imagine driving a car with a sticking brake pedal, freakin crazy unsafe.

[nihil]

It would only do it under very hard braking. Much harder than under normal driving circumstances. Though, I noticed that after a few sessions of hammering at it, it was starting to kick in a bit easier. Under normal and even spirited driving circumstances, braking performed great.

I'll be in the B7 for a couple days, they considered it enough of a safety issue to keep me in the loaner. But, even knowing how they were performing, if I ran a shop I'd have done the same just for liability reasons. The 2.0 is a bit more ballsy in stock form, that's for sure.

Along with the fresh brake booster, it'll be coming home with tinted windows. I figured there was no sense in wasting the downtime, so I had them throw on some 45% all around.

[nihil]

Well, I picked her up from the dealer an hour or two ago, and though I haven't had time to really beat the crap out of the brakes, I did get a chance to stomp on them a couple times (no events, just my own curiosity). It stops a bit shorter than before, and I can get ABS to kick in on dry asphalt now. The major difference in pedal feel is the fact that it no longer sticks to the floor (very very pleased about that). The threshold where panic assist kicks in is not nearly as noticeable as it was before, so I'm not in such a rush to get rid of it now.

Thanks everyone for your input, and thanks AoA.

Also, the tint looks sweet