A3 Brakes and Warnings

[rozel]

Hi all, I am worried about the fact that there is only one wheel where the sensor(s?) are fitted (front right in the UK case). In fact brakes are something which seem to me have avoided serious technological improvements over the past 10 years. I mean one wheel? Are we seriously to expect that all brake pads wear evenly? Then are both pads in the one wheel fitted with indicators or just one? I am willing to bet just one.

I came into this forum having had a major accident in my Mercedes CLK 320 cab the brakes on which totally gave out on me just after overtaking - no prior warning nothing! I was given to understand the brake fluid boiled dry and all cars in these instances fail completely in these instances - really?

My New A3 SportBack 1.4 TFSI 122 SE arrives in a few weeks time and have been reading the threads in this forum and just wonder if Audi technology is any different to Mercedes's.

My wife refuses to get back into the Merc now hence it's sale for the A3 and just wonder if, if the same thing happened in the A3, what the position would be? My Merc had brake sensors fitted to one pad but on all four wheels and in the event of a brake failure or deterioration at least I would have expected some sort of dash light warning. What would be the situation in the A3 if the brake fluid boiled dry?

Hope you guys can alleviate mine and my wife's anxieties

 

[veeeight]

You have an EPB Electronic Park Brake in the A3

In an emergency, pull up on the little switch, it will apply emergency braking hydraulic pressure to all wheels.

In the unlikely event that there is no fluid (low fluid warning in the dash) - it will use the electric motors in the rear wheels to apply the parking brake.

Moreover:
Regular service intervals will ensure that your brake pads aren't worn
Front brake pads tend to wear evenly across the axle
The pad closest to the piston will wear slightly quicker than its counterpart across the calliper, the sensor will be on the piston side
Brake fluid change every 3 years will alleviate hygroscopic effect, thus won't boil dry (I've very rarely come across this situation in real life)

 

[Andy1608]

How often did you have the brake fluid changed on the merc? It takes years of none maintaining break fluid for it to absorbed enough moisture to lower it's boiling point or you've had a leak and lost all break fluid.
I personally think breaks have come along way also with other safety features such as ABS and thy have saved my bacon plenty of times.

 

[rozel]

I like the sound of EPB - is this well documented in the Handbook? Other than that none of the other features mentioned in both the above posts are any different to those that were on my Merc when I got it 12 years ago. Fully Mercedes serviced so I must assume the brake fluid was changed in accordance with the service intervals. I still do not like the one wear indicator per wheel and only fitted to one wheel - a retrograde step - is this the same on all A3 models?

And even in the early days of my motoring dual-circuit brakes prevented sudden failure ocurring in the event of a brake fluid leak. But my brake fluid boiled dry and in these situations I am given to understand all cars will suddenly loose all braking.

Edit - I got out of the potentially fatal accident by stamping on the handbrake and doing a semi-hanbrake turn.

 

[veeeight]

If your brake fluid did indeed boild dry (very rare outside of track days and racing) - then one or both of the following must have happened:

1. Brake fluid with a lot of moisture in it, needed changing ages ago (Brake fluid change isn't always included as part of a service, it's normally an extra) and wasn't changed.
2. You had a small malfunction (eg: binding brakes) which you may not have noticed, but gave rise to heat, which in turn raised the temperature of the brake fluid.

I wouldn't worry too much about the brake pad wear, it is looked at every time you go in for a service, and is part of the MoT. And it's simple enough to look at through most alloy wheels.

 

[rozel]

Hmmmm - so are we being led to believe that brake pad wear is more important than a potentially extremely dangerous situation ocurring in the event of total brake fluid loss? Anyone notices that a total brake pad wear-out causes "noise" so not hard to diagnose. But brake fluid loss? I will have to check my handbook for the CLK to see if it was fitted with a brake fluid loss indicator. I would have thought it had been but I really got no notification whatsoever when the brakes all suddenly faIled.

So I am still scared about brake fluid loss, whether caused by boiling dry or otherwise on the A3 or indeed on any other car for that matter. I am not sure at all what caused the brake fluid to boil dry, that is if I can believe the garage. It was MOT'd by them last July with nothing indicated on the MOT that anything needed sorting! I smell something fishy but that is another matter. What concerns me is their statement that any car, make or model, will have total brake failure in the event of the brake fluid boiling dry. In this day and age this is not good and supports my theory that brake technology has not advanced much in the last decade.

 

[rozel]

2. You had a small malfunction (eg: binding brakes) which you may not have noticed, but gave rise to heat, which in turn raised the temperature of the brake fluid.

This maybe what happened - had no indication but surely, lets say for example a siezed caliper, I should have had some prior indication that something was wrong? So lets say a siezed caliper exists and boils the brake fluid - then I am possibly dead meat!

 

[Andy1608]

I think if you looked at the total figure of cars that have been involved in an accident on the roads from brake fluid boiling dry the number would be very minimum. It looks like to me that you've kept your service up at Mercedes but most probably not had the bolt on service of a break fluid change which after 12 years the brake fluid may boil dry if it's absorbed enough moisture.
I don't mean this to sound funny but if your scared of your brake fluid boiling dry and have a theory that brake technology hasn't advanced in the last decade I don't think you should be driving. Get a highway code from 10 years ago and check the stopping distance out and then go try it in a modern car.

 

[rozel]

Not so much being scared Andy, but I got absolutely no warning whatsoever. I am not querying Stopping Distances but rather Failure Prevention, that is what I mean by the advancement of technology - sorry if you've misinterpreted what I am saying.

If a new car's brakes can completely fail today as they can (I am being advised they can) then I say again nothing has moved on in the last 10 years.

 

[veeeight]

This maybe what happened - had no indication but surely, lets say for example a siezed caliper, I should have had some prior indication that something was wrong? So lets say a siezed caliper exists and boils the brake fluid - then I am possibly dead meat!

The indication for a seized or binding caliper is this.

You should, once a fortnight, on a straight, empty, wet road, stand on the brakes sufficiently hard to activate the ABS. If your calipers are seized/binding, you will feel the steering pull briefly, before the ABS compensates.

If all is well the car will stop in a straight line.

And I agree with Andy above. Brake technology is very advanced today, compared with even 5 years ago.

However you are looking to mitigate the smallest risk of something happening, with the increased cost of providing electrical warnings for every scenario - this just isn't cost effective.

At the end of the day, the car still has 2 discreet and separate braking systems - the Hydraulic Service braking system, and the Park Brake system. Failure of both these systems will be extremely rare.

 

[rozel]

Failure of both these systems will be extremely rare.

I agree and it was my Parking (foot activated) braking system which saved me. Nevertheless would my wife have reacted as quickly? I don't think many people would have, except skilled drivers etc.

No it was just the statement that in the event of total brake fluid loss all cars (no exceptions) will suffer complete brake failure. Dual circuits are ok for leaks but there is only one master cylinder through which all the fluid passes - so I disagree that brake failure technology has progressed in the last 10 years.

 

[cuke2u]

There must be worst thing to worry about and the chances of a brake failure owning to the fluid boiling away are so rare I think you are more at risk from a coconut falling on your head...

 

[rozel]

Lol But it happened to me last week! Really I am not sure you guys understand, probably because it hasn't happened to you. If it had then maybe you would be not so dismissive.

 

[Battlekrapz]

Fact is you need some time to recover from the terrifying experience. I understand cause i spun my car on a motorway and crashed in 500 metres of guard rails after aquaplanning at highish speed. It took me some time to stop obsessing about this accident and so it will also take time for you to start trusting your future car. Give it some time and you'll start moving on but i do understand perfectly how you feel at the moment.

 

[Itguy]

The indication for a seized or binding caliper is this.

You should, once a fortnight, on a straight, empty, wet road, stand on the brakes sufficiently hard to activate the ABS. If your calipers are seized/binding, you will feel the steering pull briefly, before the ABS compensates.

If all is well the car will stop in a straight line.

And I agree with Andy above. Brake technology is very advanced today, compared with even 5 years ago.

However you are looking to mitigate the smallest risk of something happening, with the increased cost of providing electrical warnings for every scenario - this just isn't cost effective.

At the end of the day, the car still has 2 discreet and separate braking systems - the Hydraulic Service braking system, and the Park Brake system. Failure of both these systems will be extremely rare.

I had a seized front calliper on my 53reg Z4 2 weeks ago. Started to notice the MPG was getting a bit worse and then during a fairly slow drive out I noticed shaking of the steering wheel. Stopped, noticed more dust on the left front than the others and the wheel was warmer too, so knew it was a problem. Nursed it home, calliper off, stripped, cleaned, new rubbers etc and all good as new. 1hr job in total, solved.

I've run lots of cars 10+ years old and they invariably have all had calliper issues (2x Volvo V70 rear callipers, 1x BMW E46 330d front calliper) - they just get old and tired and the rubbers perish and allow the pistons to corrode.

Ref wear indicators - modern genuine brake pads last for AGES and certainly long enough for a longlife service interval so as said, they'll be checked visually or better at each service, no problem. The wear indicator is just that, an indicator, not a life saver etc. Modern brakes are incredibly reliable.

At 12 years old your merc brakes would have been past their best unless they'd been serviced (ie callipers rebuilt) so IMHO it would have only been a matter of time until something would have needed to be done anyway.

This is the first time I've ever heard of anyones brake fluid boiling dry too.

 

[Anarch]

Lol But it happened to me last week! Really I am not sure you guys understand, probably because it hasn't happened to you. If it had then maybe you would be not so dismissive.

OK as mentioned earlier the boiling point of brake fluid is very high (230-260C) but its also hygroscopic - it absorbs moisture(thus lowering the boiling point significantly), that's why its important to replace it regularly (I do it every year on my bike). Having said that it is extremely rare for brakes to fail completely because of it - only cases I've heard about happened while driving on mountain passes. Implementing redundancy system would probably include some secondary electronic system engaging brakes. This would no doubt cost a lot - and its just too rare of a problem to justify it. Even passenger jets have either hydraulic or fly-by-wire controls - not both at the same time. Modern brake systems (if maintained correctly) are extremely reliable. So I wouldn't worry about them failing again - just make sure you pick a good garage they change your brake fluid every 2-3 years.

 

[veeeight]

.
rozel

Now you have had your A3 for a few weeks....


Have you tested your EPB emergency braking feature yet?
drive along at say 20 mph (but it can be any speed) -

Pull and hold up the Parking Brake switch

 

[rozel]

Ha!

No I haven't but will. Ironically I have just come back from a local garage where I have taken in our Mercedes B-Class. The brakes hardly exist - after spending nearly 3 weeks in the A3, I haven't listened to the Mrs complaining about them until I went to the shops in it earlier this morning.

What is it with me and brakes these days? lol

Will report back soon

 

[rozel]

Well the emergency braking works a treat! Tha k you for reminding me about this, my son and I nearly went through the windscreen lol - we were doing 30 at the time I pulled the lever up

 

[veeeight]

Jolly good, glad you've tested this out

 

[h5djr]

Reminds me that many years ago when I was an Instructor in the TA and I was taking my Army test for driving a 4-ton truck. Part way through the test on the road section I found that I had no brakes. In fact I did, but the air assistance system had stopped working which made it feel like I had no brakes. Nothing happened when I pressed the brake pedal !! I had to drive the truck back just using the gears and no brakes. I must have made a reasonable job of it because I passed the test.

 

[Andy1608]

I didn't even know it was an emergency brake so as you can imagine I'm there on the motor way fiddling away with stuff having just got the car ish, said to the girlfriend 'wonder if this works when you pull it up with it been a park brake' think her bum was twitching like a rabbits nose lol I certainly let go off it pretty damn sharp

 

[veeeight]

Everyone should try this at least once.

But perhaps not on the motorway !!! LoL

 

[MA3RC]

So pulling the electronic hand brake at speed still works? Like pulling a hand brake in a normal car?

 

[veeeight]

It actually applies hydraulic braking to all wheels, just as the foot brake does.

Give it a go!

 

[cuke2u]

I am not sure it actually does work like a normal handbrake when you put it on at speed, I believe it acts as a emergency brake and pulls the car to a stop safely(ish)

 

[cemerson]

Yes, it's described as an emergency brake feature. Don't do it with someone behind you!

 

[cuke2u]

But not like pulling the handbrake in a 'normal' car, you'd end up in a spin. I wonder what is a normal car as well?

 

[S3quatt]

But not like pulling the handbrake in a 'normal' car, you'd end up in a spin. I wonder what is a normal car as well?

Thats only in the movies LOL!

Seen it done in a mates Nova years ago when the passenger was drunk & thought it would be funny to pull it on at about 80.
All it did was write off his rear tyres by putting massive flat spots on them lol!
Being drunk myself we thought it was hilarious of course!
Im sure if we'd been cornering at the time, it would have been a very different story tho so I don't recommend it!

 

[cuke2u]

You're late into the conversation...

 

[S3quatt]

LOL so it would seem!