Complete brake failure !!

[hifi239]

Dual braking system was mandated here in the USA in 1967. I just cannot see the whole system failing. It would take 2 separate failures. My best guess is this might be related somehow to being a right hand drive car?

I've experienced complete failure of a dual braking system before. I think one way this can happen with a single point of failure is where you are repeatedly applying the brakes, and some fluid gets pumped out each time before the isolator piston kicks in, and finally, the reservoir runs dry. Then there is no braking. But as I mentioned, you should be getting dashboard warnings about low brake fluid long before that happens. Its like those people who wonder how both their headlight bulbs could blow at the same time - actually they were driving with one headlight for months, and the other one finally blew.

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[Vercingetorix]

I've experienced complete failure of a dual braking system before. I think one way this can happen with a single point of failure is where you are repeatedly applying the brakes, and some fluid gets pumped out each time before the isolator piston kicks in, and finally, the reservoir runs dry. Then there is no braking. But as I mentioned, you should be getting dashboard warnings about low brake fluid long before that happens. Its like those people who wonder how both their headlight bulbs could blow at the same time - actually they were driving with one headlight for months, and the other one finally blew.

Every reservoir with a dual braking system I have ever seen always had a front/rear standoff. You really can’t run it out of fluid, unless there is a front and back failure.

 

[Clive]

Every reservoir with a dual braking system I have ever seen always had a front/rear standoff. You really can’t run it out of fluid, unless there is a front and back failure.

well on a Taycan you clearly can ! - fluid emptied via this burst pipe when pedal was pressed resulting in no brakes at all other than regen which is very ineffective - if you have no fluid you have no brakes

that’s the fact and it’s ridiculously dangerous, these cars should not be allowed on public highways until resolved

i stress there is no sign of damage to the pipe, it has simply burst under normal operation pressure it seems - at 3yrs old that is unacceptable / clearly not fit for purpose

 

[hifi239]

Every reservoir with a dual braking system I have ever seen always had a front/rear standoff. You really can’t run it out of fluid, unless there is a front and back failure.

Yes I see that now. It is possible in my earlier experience (actually it was my wife) that the pedal went close to the floor but she never lost the whole system.

 

[d00d]

Not saying it's the case here, but it could be perceived as complete loss if the design is substantially more pedal travel required when half of the dual system fails, particularly for someone with their seat positioned where they couldn't reach the new engagement point.

 

[Clive]

I've experienced complete failure of a dual braking system before. I think one way this can happen with a single point of failure is where you are repeatedly applying the brakes, and some fluid gets pumped out each time before the isolator piston kicks in, and finally, the reservoir runs dry. Then there is no braking. But as I mentioned, you should be getting dashboard warnings about low brake fluid long before that happens. Its like those people who wonder how both their headlight bulbs could blow at the same time - actually they were driving with one headlight for months, and the other one finally blew.

there were no low fluid warnings until the failure

 

[Clive]

Not saying it's the case here, but it could be perceived as complete loss if the design is substantially more pedal travel required when half of the dual system fails, particularly for someone with their seat positioned where they couldn't reach the new engagement point.

i drove it after the failure ( VERY slowly to get to a safe recovery location) - trust me it had NO brakes at all - not perceived ! no brakes whatsoever other than the regen effort - i have raced cars to gt3 level, i know when a car has brakes or not

at 70mph i dread to think the damage a 2t plus car would do hitting stationary traffic

i’m in conversation with DVSA now - porsche may not be taking this seriously but they certainly seem to be

 

[W1NGE]

As others have said, thank you very much for taking the time to respond to all these questions. One thing many of us learned as a result of your misfortune is that there is an emergency brake in these cars. I've been on the board and other places for a year and never heard of a brake failure. Maybe others have? That would suggest maybe not a bad design but a bad part. But who knows. I apologize if you said, but on which corner was this flex line located? I would not be surprised if the part was shared with other Porsche models like the Panamera.

+1 but don't forget the emergency brake is not unique to the Taycan - all cars have this feature which have the electric switch for activating the "handbrake" for many years.

 

[f1eng]

at 70mph i dread to think the damage a 2t plus car would do hitting stationary traffic

Not trying to diminish the experience but applying the brake pedal at 70mph gives 270kW (350bhp ish) of back torque from the motors, maybe 0.4 g deceleration, even with no hydraulic brakes. The hydraulics only take over completely at around walking pace so having no hydraulics will only give absolute zero braking at very low speed.
I am still amazed if there isn't a dual system, I thought that had been mandatory for 50+ years!

 

[RehobothTaycan1]

I’ve owned my Taycan for 3 years and the only issue I’ve had is around the brakes. I’ve never experience not being able to stop and it’s always been an issue when slowing down and the transition from regen to brakes under 5 mph. I recently had the car serviced for this issue as I experienced squishy brakes and a grinding noise under 5 mph (which they think was the ABS coming on). They did a recent software update to PSM (wasn’t clear if this specific issue was part of that software update) and bled the brake lInes. Brakes felt like a completely new car after this and the grinding noise is gone.

 

[Clive]

Not trying to diminish the experience but applying the brake pedal at 70mph gives 270kW (350bhp ish) of back torque from the motors, maybe 0.4 g deceleration, even with no hydraulic brakes. The hydraulics only take over completely at around walking pace so having no hydraulics will only give absolute zero braking at very low speed.
I am still amazed if there isn't a dual system, I thought that had been mandatory for 50+ years!

maybe this is why my wife was able to slow from the higher speed but then once stationary had no mechanical brakes as fluid had all gone at that point ?

i drove it a short distance to a safe recover location and other than the very light regen it had no brakes, not even enough to feel safe to load into the recovery truck

 

[f1eng]

maybe this is why my wife was able to slow from the higher speed but then once stationary had no mechanical brakes as fluid had all gone at that point ?

i drove it a short distance to a safe recover location and other than the very light regen it had no brakes, not even enough to feel safe to load into the recovery truck

That will be it, I expect.
The hydraulics are all you have at low speed.

I have only once needed the discs at high speed, that I know of, to avoid another car, you have to be pressing on pretty hard on twisty roads for the hydraulics to kick in then I am concentrating on the road not the power meter to see how much…

 

[castadream]

Sounds like a failure of the manual brakes, not the regen braking. I've had that happen in ICE cars I've owned, only two in the almost 60 years I've been driving. One was caused by a master cylinder failure the other by a broken brake line. Once the cars slowed down I was able to stop them with the emergency brake.

It sounds like something similar where the regen braking slowed the car as it would normally but when you got below the threshold where the manual brakes take over they failed. I wonder what the equivalent of an emergency brake is on an EV?

 

[unbiased]

How can you tell whether you are using regen vs. manual braking? I always wondered.

 

[Hirschaj]

How can you tell whether you are using regen vs. manual braking? I always wondered.

Look at the power meter in the middle tube of your dashboard. The green bar shows how much regen is used for braking.

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