Grabby Brakes?

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kicker said:
The brake recalibration had no effect but replacing the 12V battery improved it immensely, the modulation on regen can be a little jerky on occasion but there is no more awkwardly lurching to a halt when moving slowly in traffic, very happy with how it is now :D

Interesting observation. I wonder if the 12 volt battery, if weak, acts as an intermittent resistor in the braking system, throwing off the responses of the brake booster by lowering the system voltage under some conditions. Given the large number of older Leafs with 12 volt battery issues, this bears further investigation...
 
There are so many stories such as yours here on the forum of strange problems and issues that are caused by an weak, old or worn out 12V aux battery.

i suspect that the grabby brakes on the second press of the pedal occurs with a weak aux. When the pedal is first pressed it causes spooling of the actuator motor forward to increase the hydraulic pressure, but then when the pedal is released there is not enough voltage left in the system (aux + big black capacitor) to drive the motor back to the home position. When the pedal is pressed the second time the hydraulic system is already highly pressurized such that even the smallest pedal travel causes a massive lock on the calipers.

One test of this might be to remove the fuse for the capacitor and test drive the braking action.

Replacing the aux battery is the same as for an ICE car, remove negative terminal first, then positive. Install positive first, then negative.
 
I just made an account and joined just to ask the same brake related issue and foundout many of you are having the same issue. Initially i thought its because of wear in pump and rings but since you are having this in 2012 also, it cannot be the reason.

At low speeds, its impossible to stop the car smoothly, feels like the brake are sucked in even with a light tough of the pedal. I was checking brake fluid pressure with a OBD tool and saw a corresponding rise in pressure with that Grabbyness. So i can safely rule out any problems below the pump (Brake fluid lines, disk, pads, pistons etc) Anyway I'm going to have a flush of brake fluids soon.

I also felt at a stop, if i released the pedal few millimetres pressure building up under the pedal so i can re apply brakes more accurately. But all that will gone if i completely taken off the foot.

I did that pressing and keeping the pedal as gard as you can for 30 seconds as mentioned initial posts in this thread and found it helped a BIT. But problem is the same.

I'm going to get a "Brake calibration" thing as instructed by my mechanic (who has fair expertise in leaf).

Will update you guys once i got it done.

Cheers!!
 
I live in Maui Hawaii and have a 2019 Leaf SV, I also live half way up a 10,000 foot mountain. I have been having the same issue with the grabby brakes. I also have a neighbor that also has a 2019 Leaf SV. We only experience the "grabby brakes" when descending the hill. It can get quite violent when trying to come to a stop from hwy speed. At first I thought that I had a warped rotor possibly because of the heat generated when coming down from the mountain. So I purchased a set of high performance Drilled and slotted rotors the help dissipate any heat generated. I also visually inspected the break pads to look for cracks or uneven wear. My Neighbor had the same issue and also replaced their rotors. We are both experiencing the same issue. Once off the hill on flat ground there is no issue, the brakes work great. I just had to have the dealer replace the Power Delivery Module, ( https://static.nhtsa.gov/odi/tsbs/2019/MC-10170015-0001.pdf ) so I had them go thru the breaks at the same time. They found NOTHING, and said that I need to install the stock rotors and see if that solves the problem. My next move was going to be to change the break pads even though they don't need it and/or to replace the tires again even though they don't need to be replaced Apparently with everyone talking about the same problem at different levels something is wrong. Because I live on a 10.000 foot mountain and drive to sea level every day my issue is a little more pronounced, as is my neighbor. I am kind of at my wits end with this. I corrected what I thought it was, then took it to the dealer sitll with no resolution. I was also thinking about the regen system issue and was hoping that the new PDM would help but no joy on that one. My last thought was possibly the anti-lock breaking system? but don't know where to go after the dealer, and we only have one on Maui, just told me to replace the stock rotors!

If anyone has any more insight on what appears to be a prevalent problem I would love to hear it!

Aloha,
plseitz
 
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