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Discussion Starter · #1 ·
Hi all,

Brief history first I have been a Leaf owner for 4 years and my second one has just gone back as the PCP had run its course. I was a leaf Ambassador during the earlier years (hi people if you remember me from Maine road) and up till 30th April I would have told everybody I spoke to how brilliant they are. I am deliberately posting this as a new thread as I find adding to existing just means facts get confused and lost.
On the 1st May whilst in a queue of traffic I rear ended the car in front because my brakes failed completely.
The only reason I stopped was because I hit it . 30 seconds earlier I was doing 70 on the motorway.
The brake pedal just went to the floor and nothing happened other than the ABS system apparently kicking in as I could feel the brake pedal vibrating under my foot.
The incident has now been reported to DVSA. and I would encourage others who have experienced similar to do the same.
The response from Nissan has been less than satisfactory. I would have been happy to help in any way but they have not spoken to me.
I note the other instances on threads of similar things happening and I can only say that this SHOULD NOT BE POSSIBLE. Its a car and it should have brakes that work ALL the time.
 

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With due respect and only commenting on what you have written, if the ABS has kicked in the brakes are working. The stopping distance at your admitted 70 mph is approx 100 mtrs, with 75 mtrs of that being the heavy braking zone. All in perfect conditions .
I await your follow up report, after the vehicle has been fully examined and tested, with interest.
 

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I am in the same boat, I have a 2015 Nissan Leaf Tekna and have had no problems with the car apart from I have just had the same happen the other day, after a run at about 60mph on a warm day (last Sunday) i hit the brakes to slow down at a junction and total failure of the brakes :eek::eek::eek:, i felt the same at the bottom of the peddle almost like the ABS was working it was really scary, luckily there was nobody in front of me else I would have also had an accident, round the next bend the brakes worked as normal :confused: I have lost confidence in the car, we have 3000 miles left and 2 weeks left before it goes back I dont think we are going to be paying any mileage as we dont trust the car.

It should be on my dashcam Ill try and dig out the footage

The cars going back to RCI at the end of this month and we wont be getting another one. @NissanGB
 

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With due respect and only commenting on what you have written, if the ABS has kicked in the brakes are working. The stopping distance at your admitted 70 mph is approx 100 mtrs, with 75 mtrs of that being the heavy braking zone. All in perfect conditions .
I await your follow up report, after the vehicle has been fully examined and tested, with interest
My understanding is that He was not doing 70 when he crashed. He said that "30 seconds earlier he was doing 70 on the motorway". The collision happen while being in the queue of traffic so the speed was much lower. Or am I missing something?
 

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Discussion Starter · #5 ·
I am in the same boat, I have a 2015 Nissan Leaf Tekna and have had no problems with the car apart from I have just had the same happen the other day, after a run at about 60mph on a warm day (last Sunday) i hit the brakes to slow down at a junction and total failure of the brakes :eek::eek::eek:, i felt the same at the bottom of the peddle almost like the ABS was working it was really scary, luckily there was nobody in front of me else I would have also had an accident, round the next bend the brakes worked as normal :confused: I have lost confidence in the car, we have 3000 miles left and 2 weeks left before it goes back I dont think we are going to be paying any mileage as we dont trust the car.

It should be on my dashcam Ill try and dig out the footage

The cars going back to RCI at the end of this month and we wont be getting another one. @NissanGB

Hi Knoxie,

Yep thats exactly what my thoughts are. Please find the footage if you can. I am not a crusader but I would really like to try to get Nissan to do something about this before one of the owners does some real harm. You fancy reporting it to DVSA? Its an online form takes about 5 mins.
Huge thanks by the way for posting
Good offers on i3 at the moment
 

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Was the road bumpy? Regen suddenly disappaearing seems to give you a no brakes feeling.

Wasn't there a recall or something about a disappearing brake pedal being related to pre crash behaviour? I'm sure it was the car deciding it was going to crash so it takes the pedal out of the way.
 

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All it takes is a bubble of air in the braking system. I'm not saying it is that but I experienced the same thing in a Polo a few years ago. The braking resumed gradually on the way home; booked it into the dealer's and no fault was found. It didn't happen again.
 

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Discussion Starter · #10 ·
There are other threads about LEAF brake failures on here. It is rare but it happens.

The reports are just like this post: Pedal goes all the way to the floor and nothing happens. Car makes an ABS noise but there is zero brake action:



Brake Failure - 2015 Nissan Leaf

Brakes Stopped Working - Almost Crashed!
Thanks for this. I would have been very happy for Nissan to take this viewpoint (that its happened before) and put us all in touch with each other so we could find a probable cause/common situation. They NEVER spoke to me.
So far it would seem to perhaps be hot weather and humidity and high speed just before.
If its happened to you please post

Was the road bumpy? Regen suddenly disappaearing seems to give you a no brakes feeling.

Wasn't there a recall or something about a disappearing brake pedal being related to pre crash behaviour? I'm sure it was the car deciding it was going to crash so it takes the pedal out of the way.
Dual carriageway into Manchester. Flat level and straight.
 

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Discussion Starter · #11 ·
I am in the same boat, I have a 2015 Nissan Leaf Tekna and have had no problems with the car apart from I have just had the same happen the other day, after a run at about 60mph on a warm day (last Sunday) i hit the brakes to slow down at a junction and total failure of the brakes :eek::eek::eek:, i felt the same at the bottom of the peddle almost like the ABS was working it was really scary, luckily there was nobody in front of me else I would have also had an accident, round the next bend the brakes worked as normal :confused: I have lost confidence in the car, we have 3000 miles left and 2 weeks left before it goes back I dont think we are going to be paying any mileage as we dont trust the car.

It should be on my dashcam Ill try and dig out the footage

The cars going back to RCI at the end of this month and we wont be getting another one. @NissanGB
Hi Again, Sorry forgot to say my car was the same model.
 

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All it takes is a bubble of air in the braking system. I'm not saying it is that but I experienced the same thing in a Polo a few years ago. The braking resumed gradually on the way home; booked it into the dealer's and no fault was found. It didn't happen again.
The failure described by @Clogman would appear to be classic 'brake fade' , considerable braking from a high speed which puts a lot of heat into the discs and brake calipers. If the brake fluid has even a small amount of water suspended within it , it can boil. Gases compress and the brakes do not work. With the second application of brakes within the stated 30 seconds there is a second application of heat and you have your result. Within few seconds as heat dissipates the fluid returns to normal and unless the brake fluid is carefully analysed there will be no evidence of why the brakes failed. This type of 'fade' can occur in any car regardless of make , It is the reason for brake fluids to be changed at specified times/mileges, something not to be ignored at service time.
 

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I haven't had any near misses, but at times I have felt that when braking occasionally there is very little force applied.

It feels as if the brakes have started to be applied, but then they disappear. This has been under normal braking, not extreme pressure where fade would occur. Coming off the brake pedal then back on usually remedies it, but it has made me feel uneasy.
 

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Discussion Starter · #15 ·
I haven't had any near misses, but at times I have felt that when braking occasionally there is very little force applied.

It feels as if the brakes have started to be applied, but then they disappear. This has been under normal braking, not extreme pressure where fade would occur. Coming off the brake pedal then back on usually remedies it, but it has made me feel uneasy.
Sounds like first thing to do is to get the fluid changed and the brakes bled and fully tested.
As usual in these threads the real issue is being clouded. I did not give full details in my original post but having gently stopped at very visible traffic lights at the end of the motorway I then joined a queue of slow moving traffic.
The brakes failed at about the third time I put them on. Car serviced by Nissan and less than 2 years old. Dont blame the fluid guys. (we could blame the air temperature but that would be speculative) I am 62 I know what brake fade is. I do realise that a lot of people will not want to hear what I am saying but please respond to my original post. I realise this is easy for me as I no longer own a Leaf nor will I ever again unless Nissan admit there is a problem and do something about it. This is what I am trying to achieve. As I have already said I would like to find some common factors among the people who have experienced this
 

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Sounds like an ABS fault to me. Yes ABS is supposed to be "fail safe" however in rare occasions a faulty ABS ECU or (more commonly) an intermittent break in the cable to one of the sensors can lead to complete loss of brakes for a few scary seconds.

I've had this happen to me personally (in a Citroen, not a Leaf) and know a few friends on another car forum that have experienced the same, so this is not something unique to the Leaf.

The ABS hydraulic control block is connected "in series" with the brake lines from the brake pedal and by default is in a "bypass" mode where the pressure from the brake pedal/booster is passed through to the brake caliper unaltered. When ABS activates on a wheel a solenoid in the control block effectively disconnects that wheel's brake caliper from the supply from the brake pedal/booster and connects it to an overflow return, thus releasing the brake on that wheel.

So solenoid activation = brake disabled on that wheel regardless of pressing the pedal. When the pedal is isolated from one of the calipers this causes the pedal to travel further down so the pulsing on and off of the brakes also pulses the pedal up and down which is what you feel when ABS activates.

In theory a faulty or malicious (hacked?) ABS ECU has the power to operate all 4 solenoids at once effectively disconnecting your brakes entirely for an extended period of time all under software control. Obviously this is a very undesirable situation so there are a lot of safety interlocks in the ABS ECU but they are all software based so not infallible.

One safety interlock is that if the ECU detects any inconsistencies between the speed reading of the 4 wheels, such as 3 wheels saying 30mph and one wheel permanently saying 0mph, even without the brakes being applied, within a couple of seconds it registers a fault, brings on the ABS warning light and disables itself - in this disabled mode it will not activate the brake release solenoids in any circumstances, and you are now effectively driving without ABS - your brakes will work fine but braking hard will lock the wheels just like any old car without ABS.

However cable faults to a sensor can be more subtle - they are typically intermittent, depending on the steering wheel angle (for front wheels) and suspension height and movement over bumps etc.

If one cable goes permanently open/short circuit (or open/short circuit for extended periods of time) then one wheel will read 0 mph and the system will safely deactivate itself. However in rare occasions vibration of the cable can cause it to rapidly connect and disconnect dozens of times a second - this generates additional pulses that have the effect of fooling the ECU into thinking that the wheel belonging to the faulty sensor is going much FASTER than the other 3 wheels.

So the ECU might think that one wheel is doing 50mph and the other three are doing 30mph. The incorrect conclusion it draws from this is that the faulty "50mph" wheel is the one that is OK and the other three wheels doing 30mph are about to lock up so it releases the brakes on 3 of the 4 wheels! :eek:

Even worse - the ABS on some cars, especially older ones, only has one solenoid shared between both rear wheels, so the rear wheels can't be controlled independently, so if the faulty wheel sensor is at the rear it results in ALL four brake calipers being released and you have NO brakes at all for a few seconds until the ECU realises that there is a fault and disables ABS. This can take anywhere from about 2-5 seconds depending on the ECU, during which time you have an accident or a brown pants moment...

Some ECU's seem to be easier to "fool" than others under sensor fault conditions. For example you would think that if 4 wheels were reporting 30mph and then suddenly one wheel reading intermittently jumped to 50mph the ECU should immediately think "that's not right" and disable itself, but apparently not, some ECU's will believe the instant change from 30mph to 50mph is valid and that the other three wheels that were doing 30mph all along are now actually locking up. :rolleyes:

From the symptoms described there's no way its going to be brake fade or air bubbles. Definitely an ABS fault.

Unfortunately it could be difficult to find/prove. This sort of intermittent fault might or might not set fault codes in the ABS ECU - when it happened to me (albeit on an older car) no fault codes were set. The only way to catch it in that case would be to have a diagnostic tool running in the car while driving, monitoring the reported wheel speed of all 4 wheels as you drive, watching for any anomalous jumps or drops in the reported speed of one wheel compared to the others...

In my case I was unable to identify which wheel sensor was causing the issue but it gradually got worse until the sensor failed completely putting the ABS light on and since replacing the faulty sensor I've never had a "no brakes for a couple of seconds" failure again.
 

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Hi Paul
Thanks for replying on my "Leaf Brake Failure" thread - that meant I got a push notification email. Sorry to hear you have had the same problem that sounds more serious than mine in that it wasn't just a startup problem, but that you had been driving for some time. I see that people are making postings here that are completely missing the point about the failure that we have both experienced - a little annoying. The post by DBMandrake is very interesting, though because he talks about wheel sensor problems, and as I mentioned in my posts, the AA man's fault analysis system showed 3 wheel sensors having errors, which didn't show on my LeafSpy error display.
I have had no further paperwork from Sandicliffe Motors in Loughborough, since they say that the "software update" they performed doesn't get the same level of paperwork compared with the expensive hardware replacement they made when I had the first failure. You probably saw on that thread that the conversation changed to talk about the CANbus and dongles, but didnt really reach a conclusion. Subsequently, the CANbus splitter cable I was using for the logger and the dongle developed a fault (several broken wires), so the logger is no longer connected, and I just sometimes plug in the dongle direct into the port to use LeafSpy. The upside of all this is that we have had no further problems with the brakes, although I still have moments of worry, and hover a foot near the foot operated handbrake at critical times.
I am happy to co-operate in any gathering of data you want in order to make a complaint to Nissan.
best regards
Tony
 

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Discussion Starter · #19 ·
Sounds like an ABS fault to me. Yes ABS is supposed to be "fail safe" however in rare occasions a faulty ABS ECU or (more commonly) an intermittent break in the cable to one of the sensors can lead to complete loss of brakes for a few scary seconds.

I've had this happen to me personally (in a Citroen, not a Leaf) and know a few friends on another car forum that have experienced the same, so this is not something unique to the Leaf.

The ABS hydraulic control block is connected "in series" with the brake lines from the brake pedal and by default is in a "bypass" mode where the pressure from the brake pedal/booster is passed through to the brake caliper unaltered. When ABS activates on a wheel a solenoid in the control block effectively disconnects that wheel's brake caliper from the supply from the brake pedal/booster and connects it to an overflow return, thus releasing the brake on that wheel.

So solenoid activation = brake disabled on that wheel regardless of pressing the pedal. When the pedal is isolated from one of the calipers this causes the pedal to travel further down so the pulsing on and off of the brakes also pulses the pedal up and down which is what you feel when ABS activates.

In theory a faulty or malicious (hacked?) ABS ECU has the power to operate all 4 solenoids at once effectively disconnecting your brakes entirely for an extended period of time all under software control. Obviously this is a very undesirable situation so there are a lot of safety interlocks in the ABS ECU but they are all software based so not infallible.

One safety interlock is that if the ECU detects any inconsistencies between the speed reading of the 4 wheels, such as 3 wheels saying 30mph and one wheel permanently saying 0mph, even without the brakes being applied, within a couple of seconds it registers a fault, brings on the ABS warning light and disables itself - in this disabled mode it will not activate the brake release solenoids in any circumstances, and you are now effectively driving without ABS - your brakes will work fine but braking hard will lock the wheels just like any old car without ABS.

However cable faults to a sensor can be more subtle - they are typically intermittent, depending on the steering wheel angle (for front wheels) and suspension height and movement over bumps etc.

If one cable goes permanently open/short circuit (or open/short circuit for extended periods of time) then one wheel will read 0 mph and the system will safely deactivate itself. However in rare occasions vibration of the cable can cause it to rapidly connect and disconnect dozens of times a second - this generates additional pulses that have the effect of fooling the ECU into thinking that the wheel belonging to the faulty sensor is going much FASTER than the other 3 wheels.

So the ECU might think that one wheel is doing 50mph and the other three are doing 30mph. The incorrect conclusion it draws from this is that the faulty "50mph" wheel is the one that is OK and the other three wheels doing 30mph are about to lock up so it releases the brakes on 3 of the 4 wheels! :eek:

Even worse - the ABS on some cars, especially older ones, only has one solenoid shared between both rear wheels, so the rear wheels can't be controlled independently, so if the faulty wheel sensor is at the rear it results in ALL four brake calipers being released and you have NO brakes at all for a few seconds until the ECU realises that there is a fault and disables ABS. This can take anywhere from about 2-5 seconds depending on the ECU, during which time you have an accident or a brown pants moment...

Some ECU's seem to be easier to "fool" than others under sensor fault conditions. For example you would think that if 4 wheels were reporting 30mph and then suddenly one wheel reading intermittently jumped to 50mph the ECU should immediately think "that's not right" and disable itself, but apparently not, some ECU's will believe the instant change from 30mph to 50mph is valid and that the other three wheels that were doing 30mph all along are now actually locking up. :rolleyes:

From the symptoms described there's no way its going to be brake fade or air bubbles. Definitely an ABS fault.

Unfortunately it could be difficult to find/prove. This sort of intermittent fault might or might not set fault codes in the ABS ECU - when it happened to me (albeit on an older car) no fault codes were set. The only way to catch it in that case would be to have a diagnostic tool running in the car while driving, monitoring the reported wheel speed of all 4 wheels as you drive, watching for any anomalous jumps or drops in the reported speed of one wheel compared to the others...

In my case I was unable to identify which wheel sensor was causing the issue but it gradually got worse until the sensor failed completely putting the ABS light on and since replacing the faulty sensor I've never had a "no brakes for a couple of seconds" failure again.
Brilliant reply. Thanks for this. It completely explains everything to me but I still wonder whether temperature or other factors are causal in the fault happening. One of the previous posts has a readout by the aa when they were called out which to my mind is completely explained by what you have said. I just wonder whether its predictable in any way. Be nice for all the owners if it was.
 

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Discussion Starter · #20 ·
Hi Paul
Thanks for replying on my "Leaf Brake Failure" thread - that meant I got a push notification email. Sorry to hear you have had the same problem that sounds more serious than mine in that it wasn't just a startup problem, but that you had been driving for some time. I see that people are making postings here that are completely missing the point about the failure that we have both experienced - a little annoying.
I have had no further paperwork from Sandicliffe Motors in Loughborough, since they say that the "software update" they performed doesn't get the same level of paperwork compared with the expensive hardware replacement they made when I had the first failure. You probably saw on that thread that the conversation changed to talk about the CANbus and dongles, but didnt really reach a conclusion. Subsequently, the CANbus splitter cable I was using for the logger and the dongle developed a fault (several broken wires), so the logger is no longer connected, and I just sometimes plug in the dongle direct into the port to use LeafSpy. The upside of all this is that we have had no further problems with the brakes, although I still have moments of worry, and hover a foot near the foot operated handbrake at critical times.
I am happy to co-operate in any gathering of data you want in order to make a complaint to Nissan.
best regards
Tony
Thanks Tony,

My dealership, who were very sympathetic, called Nissan out to inspect the vehicle but they never reported their findings to me directly. Eventually the dealership told me that they (Nissan) were unable to find "anything wrong with the vehicle" but this was obviously when it was inspected and had been switched on and off a few times.
Given that Nissan customer care can only comment on what was found there is really no point in talking to them further. Consequently I have contacted DVSA. You fancy doing the same? (sorry if you have already done it)
If the fault is on the ABS control and the explanation above is correct how can this be acceptable on any car.
Thanks again.

Paul
 
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