Complete brake failure !!

[andix]

What if the whole thing is fake?

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[alexsas]

Can I offer a theory as to what happened here? Having gone through the Audi J1 self study guide I think I know what happened.

They Taycan has a mostly brake by wire system. When you depress the brake on a "normal" car, a mechanical linkage compresses the fluid in the brake master cylinder, ignoring any power boost for the moment. In the Taycan, when you depress the brake pedal, you are compressing fluid in the brake pedal itself in normal normal cases there is no connection to the actual master cylinder. The braking ECU then interprets the pressure you are creating and determines how much regen and physical braking to apply based on the amount of pressure you are creating.

There is a backup in the event that the ECU fails, a direct hydraulic connection from the brake pedal to the master cylinder controlling the mechanical brakes allowing a minimal amount of braking, but only when the brake pedal is near the floor. It has to reach a threshold pressure in the pedal assembly to open the valve enabling this connection.

This is the tube that likely split. The ECU would see no pressure and you've lost the physical connection resulting in a total brake failure. It also explains the brake fluid on the floor inside the vehicle. (I've had a brake line split and cause this kind of total loss of braking and was only able to avoid rear ending a stopped bus by driving into a snow filled ditch.)

I'm not particularly worried about this happening to our Taycan though. There are billions of brake tubes and hoses in the world and a one in a million manufacturing defect is just that. Until another Taycan or Audi GT suffers this same issue I'll consider this a freak occurrence. If it happens a couple of more times, well, then I'll want a recall.

The practical takeaway as posted upthread is to know that the park button will initiate an emergency stop if you press and hold it.

That’s an interesting theory, but I think the OP meant the outside break pipe that goes to one of the wheels

 

[alexsas]

What if the whole thing is fake?

Given how many issues I have had in 4 months of owning “this” I tend to believe this is a true story

 

[DougFrisk]

That’s an interesting theory, but I think the OP meant the outside break pipe that goes to one of the wheels

I took his "pedal hit the floor ... brake fluid all over the floor" in post six to mean floor of the car and not on the ground.

But we're all often unreliable narrators so you could be right.

 

[WasserGKuehlt]

What if the whole thing is fake?

The thought has crossed my mind, too. There are a few “hmm” flags, we’ll see where this goes. Still an interesting thread.

 

[hifi239]

I took his "pedal hit the floor ... brake fluid all over the floor" in post six to mean floor of the car and not on the ground.

But we're all often unreliable narrators so you could be right.

I really like the brake by wire theory also, except Clive said repeatedly that the dealer found a split flex hose (the one that goes from the hard brake line to the caliper). The dealer will call that a hose, and will call the hard part a "line." Maybe there was a miscommunication with the dealer. Clive said the "nr" corner, which isn't a corner, as opposed to, say, "fr." So yes, by "all over the floor" he might have meant "all over the ground." Maybe we'll get clarification.

 

[Crick]

I wonder, will jabbing the "P" button in an emergency engage the parking brake?

 

[Crick]

I recently had the car serviced for this issue ... and bled the brake lInes. Brakes felt like a completely new car after this and the grinding noise is gone.

Same. Good source post: Brake Symptom – Brake Pedal Travel Perceived as “Too Long” Just Before the Vehicle Comes to a Standstill: Observe Specified Procedure (SY 90/21)

 

[Clive]

What if the whole thing is fake?

i wish it was !

still talking to opc / porsche gb about this ……. and the DVSA

I have photos of the pipe and the complete failure is very much fact - when i have resolution i will post them here for others reference

I’m selling the car as soon as i get it back , no way my family will drive it again, this is going to cost me significantly as it was not the plan

i’ve been a very happy Taycan owner for 66k miles - it’s been great and this is the first problem we have had, BUT it’s problem so serious it needs to be shared with other owners

 

[ct4s]

Sorry to read this - glad no one was injured.
I had complete brake failure on an old Skoda Octavia circa 12 years ago. Rare, but does happen.
It was an old car and used for skip runs, large dog and parking overnight at a train station, and only used every few weeks.
I was taking it for an MoT and hit the brakes very hard at 70mph to clean up the discs. (It was a long, straight and deserted road).
Complete brake failure. Both systems failed (think they were linked front to opposite rear).
Pedal instantly hit the bulkhead, no braking force whatsoever.
Luckily, it was manual with a real handbrake. So I managed to get to 10mph for a roundabout and the garage was 100 meters further along.
Lines failed where the metal and plastic parts meet - old age problem. Certainly wouldn't expect this on a new car.
Scrapped it.

 

[Clive]

I really like the brake by wire theory also, except Clive said repeatedly that the dealer found a split flex hose (the one that goes from the hard brake line to the caliper). The dealer will call that a hose, and will call the hard part a "line." Maybe there was a miscommunication with the dealer. Clive said the "nr" corner, which isn't a corner, as opposed to, say, "fr." So yes, by "all over the floor" he might have meant "all over the ground." Maybe we'll get clarification.

sorry if not clear

fluid was on floor / ground ( ie the road not inside the car). it’s the front passenger side flex hose that has burst, there appears to have been. no impact etc

i know this shouldn’t cause complete failure …… but it did and that’s what needs serious investigation imo

 

[whp03]

Losing all brakes is definitely a horrifying experience. At least Taycan has fairly strong regen braking (way stronger than Tesla) which I assume is a good backup at higher speeds. Maybe I'm just overly paranoid (cutting brake lines is a movie classic) but I hope this wasn't sabotage. Porsche should be able to detect if that's the case (and call the police if they suspect it).

I find it the string of comments about the Taycan’s regen braking being “strong”. We have a ‘21 Taycan 4S and ‘23 VW ID.4. The VW regen in B (driving BRAKE mode) will slow you to a stop. The Taycan in regen would take us more than a half mile to slow in a meaningful way. Maybe our regen isn’t fun functioning properly. Yes, we can tell when regen is on vs off, but it almost sounds by some posts that regeneration could stop the car? In our case, never. I suspect feedback to this post will lead us to a service appointment.

 

[whitex]

I find it the string of comments about the Taycan’s regen braking being “strong”. We have a ‘21 Taycan 4S and ‘23 VW ID.4. The VW regen in B (driving BRAKE mode) will slow you to a stop. The Taycan in regen would take us more than a half mile to slow in a meaningful way. Maybe our regen isn’t fun functioning properly. Yes, we can tell when regen is on vs off, but it almost sounds by some posts that regeneration could stop the car? In our case, never. I suspect feedback to this post will lead us to a service appointment.

You are using Tesla's definition of "regen", applying it to VW. Teslas only regen when you take the foot off the pedal. Tesla brake pedal controls the mechanical brakes directly (so if you are pressing the brake pedal, you are stopping with mechanical brakes). Taycan on the other hand regens (or recuperates, per Porsche terminology) both when you take your foot off the accelerator and when you press the brake pedal. The latter is much stronger, taking your foot off the accelerator enables very small amount of regen. Tesla maximum regen is ~60KW, Taycan 270KW. Of course to reach that 270KW of slowdown you will have to hit the brake pedal. Putting this much regen on the accelerator lift would translate to horrible experience (imagine your car auto slams on brakes when you lift off the accelerator, or simply imagine 5x the braking force whatever you have today on the ID.4 when lifting off the accelerator). Heck, every time you lift your foot to move to the brake pedal, you'd already be braking very hard.

 

[DougFrisk]

I find it the string of comments about the Taycan’s regen braking being “strong”. We have a ‘21 Taycan 4S and ‘23 VW ID.4. The VW regen in B (driving BRAKE mode) will slow you to a stop. The Taycan in regen would take us more than a half mile to slow in a meaningful way. Maybe our regen isn’t fun functioning properly. Yes, we can tell when regen is on vs off, but it almost sounds by some posts that regeneration could stop the car? In our case, never. I suspect feedback to this post will lead us to a service appointment.

One pedal/bumper car driving is NOT REGEN!

Regen is using the electric motors to slow the car. When you press the brake pedal in the Taycan it uses regen up to 290 kilowatts which is pretty damn ferocious braking, only if you need to brake harder than that does it use the physical disks. The bumper car regen on the tesla s is only 60 kilowatts.

Bumper car mode exists in many cars because Tesla and a few other companies were unable to mix regeneration and friction braking on the brake pedal so they initially moved all regen to the accelerator pedal. Then they spent years telling people what a great efficient idea it was instead of admitting it was essentially a hack so they could have some modest regen.

Coasting (the default in the taycan) is more efficient than you can ever be with regen on the accelerator pedal.

The maximum round trip efficiency of regen is about 60%. If you are traveling at 60; then use regen on the accelerator pedal to drop to 40 and then accelerate back to 60 again it's a net loss. If you are traveling at 60 and coast, there's no net loss in the electrical system.

Just say no to

 

[d00d]

J1.2's even stronger regen makes coasting to scrub off speed slightly less efficient than using off throttle regen.

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