Intermittent Brake failure on 458

A friend had same thing happen.
Approaching roundabout and lifted to apply brake. Car kept accelerating. No brakes (brake pedal hard). In these few seconds he had to swerve like a maniac to avoid colliding with other cars. He was about to ram it into some parked cars to avoid the next intersection when the throttle shut and brakes worked again as normal.
Before anyone asks, he had no time to turn car off and no, the floor mat was not stuck on top of the pedal etc.
He pulled over, turned car off, while being abused by everyone and emptied his pants.
Turned car back on. Acted as normal again. So reluctantly drove car home very slowly and rang F to come and pick it up.
To cut a long story short, F said nothing wrong with car. I think they offered to change some parts but as they could not identify ANY problem they would be just guessing. He refused to ever drive that car again or any other 458 they offered as exchange, as it could have the same problem. Car was resold by F and is back on the road! Ticking time bomb.
He will never buy another F car again.

One of our discussions, also discussed with the dealer, after this was imagine what would have happened if he had hit another car and everyone was killed. From all witness accounts he would have been seen as this crazy F car idiot driving like a lunatic who caused the crash. Police give car to F for testing. F say nothing wrong with car etc. So he goes to his grave as causing the crash.
Or, crashes car and "explains" to police the car accelerator just jammed on..."sure mate, sure". Again F examines car and says throttle is just fine...

He is not on F chat and when I told him about another 458 with same problem, he asked me to tell his story.
He may sign up and post to confirm or add to the above.
I have heard of 360's and 430's revving uncontrollably too. These cases are documented here on F chat. So far my 430 has never done this.

 

Maybe this should be in the 458 section?

 

ABS failure. Maybe just a sensor. Yep. That's how it feels.

 

Don't know about acelerater but abs brakes can be put into "ice" mode for lack of better term where you loose all brake function like your car is on ice when the abs system is confused. It is possible that there is a set of conditions that trigger this. GM says this does not exist in the C5 corvette but I can show you how to trigger it at speed in a C5 corvette. We racers know this problem well and the problem has costs us tires and sometimes a car if it happens near a wall. We know exactly how to trigger it in vettes and I am sure other enthusiasts know how to trigger it on their cars. Nobody in the industry seems to want to acknowledge this hole in abs systems. Remember automated systems don't have to work perfectly they only have to work better than humans and they get implemented.

 

This happened to me with a 458 rental a few years ago and nearly went through an intersection.

Some people were saying the brakes need to be heated but the pedal felt super stiff like the assist wasn't working.

 

Wow, a scary problem!

Prompted by fatbillybob's tip, I did a quick Google on "abs ice mode" and sure enough there are tons of references to this problem associated with all makes of cars including Lotus, Nissan, GM, Mazda, BMW...etc.

Here's the most interesting comment I found so far, from someone who discussed this problem back in January 2012 on a (Nissan) 370 Tech/Track forum:

"I just spoke with Bosch and with the head of their major west coast distributor

Not going to quote anyone directly but basically the theories discussed in this thread are correct. The DOT approved versions of Bosch ABS induce ice mode when the wheel rate sensors detect variation across the four sensors. I am not clear if it is front/rear overall or any one wheel or both, nor did I find out what % difference the computer looks for nor timing involved in the algorithms... but it is a safety mode designed to help in the majority of street situations... hard to blame them for that

There are two systems available for dedicated track vehicles. One produced by Bosch and one produced by Continental. These systems are only provided for vehicles not used on public roads and purchasers are required to sign a waiver that is kept on file with the mfgr. The systems are sold through distributors. The Continental system is apparently a modified BMW ABS that is not configurable. The Bosch system is a bottoms-up race ABS with config options. Bosch has two major US distributors, one east coast and one west coast. The west coast distributor is Brian Sekata with MS Electronics.

I realize this is not all that helpful for those of you that will keep your cars street legal. Sorry, I have nothing to offer you folks. The only possibility I can think of is to find someone that can crack the computer and re-write the code... but then there is an issue of liability and intellectual property

For anyone reading this that has a dedicated track Z (either 370 or 350), it may be possible for us to work out a group buy on Bosch Motorsports ABS systems. I have no commitment from Brian or from Bosch, but they are interested in starting the conversation with us and asked me to carry the idea forward. If there are enough of us willing to sign that waiver, there might be a break off the system price... as many of you know, it is $10K today ... but what if it were $6K ??? better braking performance and safe guard against ending up in a concrete wall... the system is also highly configurable - from the cockpit you can adjust proportioning and how the ABS reacts

In any event, please spread the word if you know anyone else with a dedicated track Z"​

Another comment from a different Internet discussion mentioned ABS systems getting confused if the wrong (nonstandard) sized tires are used and driven under certain situations. Other people suggested risky situations include when braking hard while driven over very rough roads with tires hopping over the surfaces. Plausible.

Another problem that may be related is if you try to pump the brakes when ABS is active. Apparently, this can deplete the vacuum assist and that obviously would make things a lot worse. There's no advantage to pumping ABS brakes as the ABS system is already detecting and mitigating impending slippage for you. At full throttle (WOT) the engine also generates no vacuum, again making things a lot worse if you had the pedal floored just before pumping your brakes. If you lose vacuum, just stand on the brakes and shift the transmission into neutral. Don't turn off the engine.

There are many other Internet references to this problem, with all sorts of scenarios and theories. I'm not that informed on brake systems but I think the Bosch comment is likely the most telling. Hopefully, more information will trickle in on this surprisingly common problem. There has been quite a few reports on FChat of Fcar drivers running into "no brakes" or "zero braking" situations thinking the problems are due to breaking-in their CCM brakes which may be an entirely separate braking performance issue.

Looks to me like more good reasons to turn off ABS (if possible) when on the track.

 

Terrifying to say the least.
Glad everyone is ok

 

ABS was originally developed for aircraft, and then adapted and eventually mandated for cars. Looking into the stats seems to have some controversy whether it is substantially helpful or not.

A 2004 Australian study by Monash University Accident Research Centre found that ABS - http://www.monash.edu.au/miri/research/reports/other/racv-abs-braking-system-effectiveness.pdf

Reduced the risk of multiple vehicle crashes by 18 percent,
Increased the risk of run-off-road crashes by 35 percent.

 

Any ABS vehicle could have encountered this and the owner's resolution sounds reactionary. If the car gets into a sliding situation, a more sensitive ABS system will free the brakes from lock, even when it is what you want. Snow, gravel and sand all can be problematic for ABS. You can easily experience this scenario yourself at low speeds, especially on a slushy road or in some gravel.

In my worst case example, my car (Acura Legend) was bumped at speed and entered a shallow angle slide. Flooring the brakes did nothing because they kept releasing any lock. The result was a high speed front end encounter with a 12-foot concrete wall. I was uninjured, but car was totaled. This is why car makers provide for ABS disconnect switches, so one can prepare for driving on an intended surface - gravel, snow, slush, sand, or the track.

 

My mechanic told me about this on a California. The assist just didn't.

He didn't have nice things to say about the technology..

 

Terrifying.
I have had one experience with ABS that I would like to share. 2002 Alfa with Bosch ABS.
Late in winter an occasional squeak from the back alerted me to a possible problem with left brake. No overheating of brakes.
A week after this symptom I take an exit from the highway. Road is perfectly dry. During braking, a road irregularity activates ABS fully with mentioned symptoms: hard pedal, ABS on fully and no deceleration at all. Tested this later again, the same happens.
After investigation, the wheels turn freely even shortly after hard brake application. The left rear drags little more than the rest causing the squeak. It turns out the caliper was binding the pads slightly because of road salt. Only minimal though.
After the stuck pads were freed by sanding rust, copper greased and reassembly, problem is gone.

My theory after this experience is the following. ABS works by pulsating the brake. If there is any delay in especially the release of pressure, the ABS system will continue lowering brake pressure, far more than needed, leading to an unexpected and near total brake failure experience.
It is still not clear to me why the total braking of the car suffered because of only a rear wheel issue, but it most certainly did lower said braking performance of the whole car far below acceptable levels.

 

The only thing I could think of is that it is probably a matter of duty cycle, and that that duty cycle for that single wheel is somehow used troughout the system:

Normal braking is 100% duty cycle, full ABS perhaps 70 on and 30 off.
However if that 30% 'off time' of the brake fails to deliver the expected result, the computer may lower the duty cycle accordingly, to 50/50 or perhaps even 20/80, resulting in very little "on time" for the braking.

It depends on how the computer measures what duty cycle is required. My guess is that it expects the brake to be released directly after dump valve actuation. If there is a slight delay in release because of something binding (or very little surface traction combined with wheel inertia), it will result in longer 'off times', longer opening of the dump valve and hence a much further decreased duty cycle than normal. If this duty cycle is applied partially or in full throughout the system it would explain it.
Obviously this is a theory, I have not enough knowledge of that Bosch ABS (same as on E39 and E60 BMW as I have been told) to substantiate - although I would like to!

 

This has happened to me multiple times. Most notably in a PU truck. No load in the back,begin braking,hit a bump,the rear axle hops up and the system kicks out. Feels like no brakes at all as you jam your foot to the firewall trying to get slowed down.
In a car I have had it happen when you stab the brakes causing weight transfer and a light rear end.
My solution is to press on the brakes like squeezing the trigger on a gun. The vehicle settles without a nose dive and everything is fine. Unless the car happens to hop over a bump.
Happens on snow and ice too. So I get off the brakes and reapply gently.
Of course braking should be the 2nd thing going on after or simultaneously looking for an unblocked route.
I realized I could outbrake an abs system at driving schools on a very slick surface. Instructor says was watching speedo and drops to zero and you are easing up and steering. Yes but with the system OFF I just lane changed back and forth while braking and stopped in a shorter distance every single time without the abs on. I do a better job by feel. Sort of learned to hit the 13% slippage mark by feel.
It think it would be best to teach/learn threshold braking. I learned before ABS.
Allegedly a four channel system cannot be beat?
Your results may vary. I always have in mind an out. Had my 575 on a track. Suprised me how early abs came on. Could brake later and shorter by staying out of abs and gently pressing on the brakes. Lots of dive in a GT car when you stab the brakes.
I'm an old guy that learned how to threshold brake by feel and use a brake bias knob.
GTS Bruce

 

Very good description, eberro.
Your expectation of the vacuum check valve matches perfectly.

Drivers feel ABS pulsing through the pedal. If it's just a hard, firm pedal, with no pulsation, and you've just gotten off the accelerator, it indicates the vacuum check valve on the brake booster may be faulty. This is a mechanical device which will be located on the brake booster with a vacuum line running to the engine.

Normally, the check valve makes sure your booster retains the highest vacuum level the engine has produced in recent times (which will happen when you let off the throttle and the engine produces a lot of vacuum behind the closed throttle plate). If it fails, your booster is exposed to whatever level of vacuum the engine is producing at the moment, (which will be less than under decel), and can be all over the map with electronic throttle pedals.

When the throttle pedal is released, it takes a moment for the vacuum the engine can once again provide to suck the booster down to a higher vacuum level again and restore normal brake pedal feel. Until that happens, while you have reduced vacuum assist, you have to push harder on the pedal. The mechanical brake system is still functioning, from pedal to master cylinder through the ABS module (which is just sitting there because you're not braking the wheels hard enough to lock them), to the calipers & pads.

FMVSS 135 specifies minimum brake performance requirements with a failed booster, and expects the driver to push on the pedal with a force of 112 lb.

 

This problem seems to be more common on the 458 than previously acknowledged.

 

Take your car to the dealer.. have them bleed the brakes.. sounds like it's air int he line. Then bed the pads properly.

 

One thing to watch out for with CCM brakes is heavy application when the brakes are cold.
That's the reason for warm up prior to racing. After an initial cold start up, you can have very limited brake grab until the brake warm up is achieved. You can speed up the brake warming procedure by doing a few gentle (riding the brakes) low speed brake applications. There's a significant amount of engine braking available with the 458, and if you are having an issue; you can easily scrub speed by doing a double downshift with the transmission.