Complete brake failure !!

[bluesky]

That must have been very frightening and glad everyone was safe.

The thing all Taycan drivers should try to remember in case of a failure emergency is that the emergency brake (regen only, does not use conventional brakes, is intended for conventional brake failure) is:

hold the P button to brake, release to stop regen braking.

The owner’s manual warns that this will be “severe braking”, presumably the max the system is capable of.

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[daveo4EV]

loss of fluid onto the "floor" would indicate a leak of the master cylinder or brake line(s), calipers - while loss of braking is a serious issue - this is highly unlikely to be a design defect - my guess is some sort of damage to the braking system causing a fluid loss - if it is the result of damage to the system this could happen to any vehicle.

good luck with repairs and sale - but I doubt this is a systemic issue with Taycan until there is further evidence.

 

[Tooney]

Report a serious safety defect - gov.uk

 

[DerekS]

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

 

[bluesky]

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

see post #16

 

[Tooney]

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

 

[Marmolata]

Tooney, thanks for posting that!

 

[Marmolata]

OP, if you feel it was as serious as your posts suggest, you should call police at the time and file accident report and lmk what happened so there is an official report on record. Then you can take that report to Porsche and the appropriate government agency

 

[hifi239]

I’m so sorry! I would think Porsche GB or Porsche DE would be interested in looking at this car. Please call them a addition to all the reporting stuff. No hydraulic brake system can work without fluid. Modern systems have an isolator valve that is supposed to prevent a complete failure if one of the lines fails. I’d be stunned if the Taycan omitted this. But surprisingly, even in modern systems, a slow leak can draw down the level to the point that the brakes don’t work. I’ve had that happen due to a rusty brake line in 2009 Merc. That should, however, have put a message and light on the dash about low fluid. I suppose it is possible there is a place in the system where a blown line instantly results in a complete failure. It appears that what happened. Thanks to bluesky and Tooney for RTFM for us!

 

[irrelevant]

I'm curious what the system logic is behind this. I'd assume the car would go to max regenerative braking down to the point where deceleration would taper off to the point where the mechanical parking brake system be more effective by locking the rear wheels up to complete the stop.

Next, I wonder what the process is for moving the car from that point? Would selecting "D" allow the car to be driven? There must be some process to allow this, but I can see the corporate liability-focused attorneys arguing the car should remain disabled wherever it stops once an emergency brake application is performed. That could be far from ideal, depending on where the emergency stop was completed.

I guess there's one way to find out...but I'm not willing to do it. ?

 

[OzzieT]

@Clive that is very serious and scary. I recently submitted an online booking to my dealer for the one year service check. As part of that I was asked if I had any issues and I said that my brakes were rubbish - that is spongy and unresponsive especially at low speeds. I was called my dealer 2 hours later and the car was in for service two days later.

As it turns out I had "SY4701N fault - bled brake fluid and applied software update". I'm driving a different car now. I suspect your issue and my issue are completely unrelated but thought I would share.

 

[hifi239]

I'm curious what the system logic is behind this. I'd assume the car would go to max regenerative braking down to the point where deceleration would taper off to the point where the mechanical parking brake system be more effective by locking the rear wheels up to complete the stop.

Next, I wonder what the process is for moving the car from that point? Would selecting "D" allow the car to be driven? There must be some process to allow this, but I can see the corporate liability-focused attorneys arguing the car should remain disabled wherever it stops once an emergency brake application is performed. That could be far from ideal, depending on where the emergency stop was completed.

I guess there's one way to find out...but I'm not willing to do it. ?

It is likely not regen at all. It is likely similar to ICE cars that have an an electric parking brake (EPB). The button activates an electric actuator that applies the mechanical brake pads to the rear wheels. Have you activated the HOLD mode and felt the thunk when it releases? The manual says with the car moving, you can hold down the P button and this will trigger the electric actuators. When you release the P button, they will retract. I think you could try it at low speed in a parking lot to feel the effect, like you might with an ICE cable parking brake.

 

[fullmetalbaal]

That must have been very frightening and glad everyone was safe.

The thing all Taycan drivers should try to remember in case of a failure emergency is that the emergency brake (regen only, does not use conventional brakes, is intended for conventional brake failure) is:

hold the P button to brake, release to stop regen braking.

The owner’s manual warns that this will be “severe braking”, presumably the max the system is capable of.

I think this is about the only useful post in this thread.

 

[irrelevant]

It is likely not regen at all. It is likely similar to ICE cars that have an an electric parking brake (EPB). The button activates an electric actuator that applies the mechanical brake pads to the rear wheels. Have you activated the HOLD mode and felt the thunk when it releases? The manual says with the car moving, you can hold down the P button and this will trigger the electric actuators. When you release the P button, they will retract. I think you could try it at low speed in a parking lot to feel the effect, like you might with an ICE cable parking brake.

I can't imagine the car would only apply the parking brake at 80 m.p.h., when regenerative braking is available, and probably more effective at that speed.

 

[whitex]

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).

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