[mihaiilea]

I had a brake failure on track, something went wrong because no matter how hard i pressed the pedale of the car, it didn’t lost speed at all so I hit some barriers.
It is very strange that the car seemed to lost ABS and DSC at that moment. I found that 80.000 cars made for US, and 370.000 cars globaly have a defect at integrated Brake.
https://www.caranddriver.com/news/a4...nction-recall/
https://uk.marketscreener.com/quote/...lems-46251202/
Also 2 weeks before the incident i found some leaks under the car, it was a yellow liquid. I went with the car at the dealership and they have told me the car is ok, they checked it only for 5 minutes.
Anybody has any idea about these problems and what went wrong?
I would appreciate any idea or information.
Thank you in advance for your help.

[lizardx]

From the photos it could be brake fluid. Brake fluid is a bit of acidic and its easy to recognize if it comes into contact with your hands by how it feels.

Brake fluid can also boil on race track, rendering your brakes ineffective.

DSC works in conjunction with ABS unit - so without a functioning ABS, DSC can't operate.


Did you do an error scan? Drop in hydraulic pressure of ABS system should most likely be stored.



My hypothesis would be you had a leak in ABS/braking system; brakes worked until the fluid volume dropped too low, and brakes stopped working.

[mihaiilea]

[QUOTE=lizardx;31127243]I have 10 years of going on track with diffrent cars. Never had any problems.
Also the incident was after staying parked for 40 minutes, go for a warm up lap very slow and start a new lap, at the third braking point i have lost the brakes.
I never do more than 1 hard lap, then cooling for a lap and then i go and stay out at least 30 minutes to be safe.
The car also had the brake cooling air ducts covers removed for better cooling.
The tyres also where at 2.4-5 bar, 52 degress celsius.
I could not understand the situation. The car is curently at the dealer. So i have no acces of reading codes.
I feel that it was more a software error or because of the integrated brake system.
Thank you for your answer!

[CMW33]

Hard to weigh in without knowing more. The G80 M3 doesn't seem to be covered by the brake recall you're pointing to in your post. Describe the brake pedal when the incident occurred. Did any warning/error lights pop up at or just before the shunt?

Without knowing more, overheated brake fluid is a top potential culprit, followed by possible human error.

[mihaiilea]

It was on a normal lap at max 80% after 40 minutes beeing stoped. The car lost 60 km/h in 200 meters from 160 to 100 km/h. That is not a human error.
In 125 meters the car should stop from 200 km/h to 0.
I wish you could never experience that. It is a car problem 200%. The brake booster and integrated brake is the same in a lot of cars.
https://www.carscoops.com/2021/02/20...raking-issues/
It is not the first time for bmw m3!

[myaghi]

After the crash did you check the brake fluid level ? Also when you pressed the brake, did some errors / messages appeared on the dash ?
Did your brake pedal went all the way to the floor when you pressed it?

[mihaiilea]

It was happening so fast... The brake go a little deep from what i have felt. The most interesting thing was that when i touch the brake the car moved under braking ( left right) and my feeling was that front tyre on the driver side was blocked like Abs is not working.
I had a message on the driver front tyre that it has low pressure with 10 seconds prior, but the tyre had 2.5 bar ar 5x degrees, now cold the tyre has 2.0.

The problem is the car has Brake by wire, so you don’t have a connection like in the older car’s. From the pedal to the booster you only have a wire. And the feeling of the pedal is made by a vacumm.
I didn’t look at the liquid after the crash.

[Ximian]

Sounds like ABS "Ice mode" that's written about with some cars. Did you try pumping the brake pedal when the car wouldn't slow down?

Overheated pads would also not let the car slow down quickly enough. Were these the stock brake pads?

As for the 52 degrees Celcius tire temperature, did you get that from the tire pressure monitoring screen? If it's from the TPMS, that's an air temperature rather than tire surface temperature. 52 degrees C isn't particularly warm for track use so that's not an issue.

[mihaiilea]

The tyres are Michelin 4s so i prefer staying around 50-55 degrees when i start a lap to have enough grip at the end of it.
The intresting thing is the car brakes worked perfectly until that moment, the disc and the pads look normal, this was the 3 rd time on a track with the car.
And the brakes where really good for the first corner.
It was like the pedal was disconected from the brakes, i lift a little and than reapply but nothing change. The car was like a torpedo.
The thing is it felt like the car didn’t even try to stop at all.
The dealership is not even looking for a potential problem, i could not understand why is so hard to tell the factory looking after all the data they have! Maybe they can find an answer about what was going on! Thank you for your feedback!

[fl1by]

Could the brakes have been fine and a coolant hose failure or other fluid on the track have simulated "no brakes"?

[mihaiilea]

That is not a possibility, because other 40 cars from the event go past me with no problem and the track was open for a few hours from my event. The track look perfect and clean. Also the grip level was very good in that particular day.

[thopwood4]

This is why you always give a little tap on the straightaways to pump up some pressure and make sure they are there.

[mihaiilea]

The car has leaks, it has only 10 months an 11466 km. So it is quite not something normal. Anybody can be in my place and i wish nobody will ever be. The quality of the things is getting worse. We have to find solution. I had so many cars and never has an issue. It is what it is…hope someone will find the hole problem. I did my best trying to find out.

[Ximian]

Originally Posted by mihaiilea

Anybody can be in my place and i wish nobody will ever be.

That's why reputable track organizers in the US require track inspections to make sure there is nothing obviously wrong such as fluid leaks. Some events do not allow stock brake fluids or stock brake pads, but require track fluids and brake pads. Find a shop that specializes in building race cars or something along those lines to do your track inspections.

The quality of the things is getting worse. We have to find solution. I had so many cars and never has an issue. It is what it is…hope someone will find the hole problem. I did my best trying to find out.

The quality of certain parts, specifically the brakes, has improved drastically. Based on the pictures of the brake fluid reservoir, there was no brake fluid leak. At this point, that fluid you took a picture of on the white floor doesn't even look like brake fluid.



Either garbage juice or urine. Under what part of the car would this have been?

[mihaiilea]

Near the front driver tyre was the leak. It was very corosive. Under the reservoir we also find brake fluid. So it has leaks.

[Ximian]

Originally Posted by mihaiilea

Near the front driver tyre was the leak. It was very corosive.

Take that wheel off and look around the brake caliper and the brake lines. I've only seen it as clear fluid, but could even be a leaking strut. For a leaking caliper, that fluid would end up on the wheel.

If there is no evidence of a leak, it's not brake fluid. The routing of the har brake lines and that they're metal makes it unlikely that it's a leak from them without some sort of damage.

If you want to test it for a leak, park the car, leave the engine on and idling, then repeatedly press down hard on the brake pedal and hold it each time for several seconds. After several minutes of that, the pressure on the brake fluid would let it find any small holes to leak out of and you should see brake fluid on the wheel(s) or ground if there is a place to leak. Look under the car first for fluid before moving it so you can exactly figure out what part of the car the fluid is over.

[Ximian]

Originally Posted by mihaiilea

Under the reservoir we also find brake fluid. So it has leaks.

That's normal. Everybody spills fluid when filling it up and some people fill it up to the maximum level which isn't ideal for track use as it could be considered overfilled. Venting and "sloshing around" can be expected for a full reservoir with track use.

Perhaps someone topped off the brake fluid, spilled it on the reservoir, and the fluid followed the path to a drain ( behind the driver's side front wheel). It's the same drain as in the corners under the hood, by the windshield.

Previous generations had an issue with a brake vacuum sensor which would cause a limp-mode inducing code to be thrown, but I don't think it's the same for the G8x Ms.

[mihaiilea]

The car was untuched from factory. It had only 2 oil changes. So nobody touched the brake fluid reservoir. The dealer will make an investigation.

[CMW33]

Sounds more like you're trying to build a record for litigation. Hire an attorney if you feel confident there is some sort of brake system issue. Based on what we've seen so far, I can't rule out human error or overheated brake fluid.

[Ximian]

Originally Posted by mihaiilea

The car was untuched from factory. It had only 2 oil changes. So nobody touched the brake fluid reservoir. The dealer will make an investigation.

2 oil changes isn't exactly untouched. Not sure how service is handled in your location, but here I've seen dealership that would top off any fluids that are low during service while the car is under warranty. Also inspections would check the brake fluid level which can also be done by removing the cap.

So far you only have a tiny bit of brake fluid on reservoir which does not indicate a problem. Even if the cap on the reservoir was removed, your brakes will still function so a tiny leak there isn't an issue.

[Ximian]

Originally Posted by CMW33

Sounds more like you're trying to build a record for litigation. Hire an attorney if you feel confident there is some sort of brake system issue. Based on what we've seen so far, I can't rule out human error or overheated brake fluid.

If that's the case, it isn't going to work. Nobody warranties the performance of parts on track.

The odd thing is that there's a lot of information posted about mostly useless facts instead of the things that would be helpful in getting pointed in the right direction.

Was there a recent track inspection? What is the condition of the tires? What brake pads are installed? Howd How many sessions has the car done that day? Were there any leaks where the car was parked at the track between sessions? Do you have a manual transmission and were actually pushing down the clutch pedal instead of the brake?

[mihaiilea]

The car is in perfect shape. The tyres are 5 mm not even worn. Also the fluid looks crystal clear like in a new car.
I speak with the dealer they never touch the brake fluid and the coolant.
The car has the brake in inspection and one oil change done by me at the dealership after 7500 km because i want to keep the car for a long time.
I speak with an auto forensic expert and after seeing the images and videos it is crystal clear the car had an brake failure and not even had a deceleration.
The car never did more than 1 fast lap at a time( warm up lap slow 50%, lap, cooling ( not even touching the brake for a lap only dowshifts) , 40 minutes break at least in the pit lanes from session to session. The car had only 2 fast laps( 4 laps very slow) in 2 hours.
The disc are in great shape and the brakes pads ar at 50% after 11466 km. No brake noise, no vibration, no squealing, not even a sign of something not normal.
So something is there, the problem is not with the disc or the pads, or liquid.
The problem is about the pressure in the system, maybe the car could not engage the calipers, or maybe it has air in the system.
Nobody knows in these moment what is the cause.