Has anyone had an independent mechanic replace the brake master cylinder??

[rwherrick]

Hi,
I bought one of the earliest Nissan Leafs (2011, S/N 000445), and in addition to having rapid failure of the battery pack, it had grabby brakes from the start of the second year. In June, I got Nissan to do "routine maintenance" on it, and it started leaking brake fluid after that. A few weeks ago, it started having the VDC warning light and the brake system warning light come on when the car started. I took it in to Nissan, and they told me that to fix it, they would need to replace the brake master cylinder, and were glad to do it, and it would only cost $3718.63, in addition to the $255 they charged me to look at the car. Given that the car only has a trade in value of $2213, or a private party resale value of $4083, this didn't seem like a good investment to me. I called Nissan to ask for after-warranty assistance, and made the case that this should not be a normal repair expense for a car of this age, but they said they do not provide any after-warranty assistance for cars older than 9 years, regardless of the circumstances. I would be tempted to get a brake master cylinder from a junkyard, and have an independent repair garage install it (Nissan won't touch it), but the repair looks so complicated, I've only been able to find one post where someone did that, and it didn't sound like it went all that smoothly. (see part by bluelightning32 in the middle of page 2 at https://mynissanleaf.com/viewtopic....ghtning32+brake+2011+leaking&start=10#p511417)
Has anyone else either replaced the brake master cylinder, or had an independent repair shop do the work? If yes, was the shop able to do the re-calibration, or did it need to get towed to Nissan after the install was complete? It seems like a shame to scrap out a car with under 85,000 miles because Nissan failed in "design-for-maintainability," but that does appear where this is headed at this point. In case anyone is interested in the details, the brake master cylinder is officially called the "electrically-driven intelligent brake unit", and its removal and installation is detailed starting on page BR-261 in the Nissan Leaf repair manual listed here (https://www.nicoclub.com/service-manual?fsm=Leaf/2011/br.pdf). The repair looks incredibly complex, and I can see why nearly all independent repair shops would shy away from it. It's a shame Nissan didn't make something simpler, with a vacuum brake booster, that could have been replaced for a normal cost.
Thanks for your help,
Bob

 

[nlspace]

Yeah it's crazy complex to put an electric motor with a ball screw actuator inside a brake master cylinder, plus a big ass capacitor to hold charge in case the 12V goes out. Mitsubishi uses a vacuum system and just runs a little pump motor as needed to keep a vacuum accumulator charged.

Its too bad they messed with it and got it to start leaking. i'd be tempted to try to back the motor off and disable/disconnect it and just use manual force for the brakes. The 17 steps in the removal procedure don't seem anymore complicated than doing a vacuum system M/C replacement.

 

[rwherrick]

Mitsubishi uses a vacuum system and just runs a little pump motor as needed to keep a vacuum accumulator charged.

Using a small vacuum pump, and re-using existing vacuum brake boosters is probably how they should have done it, and then it would have been a repair that could have been in the hundreds of dollars, rather than several thousand dollars.

Its too bad they messed with it and got it to start leaking.

At the previous "routine service", I had asked them to purge the old brake fluid and bleed the system, which they said wasn't called for by the service schedule, but I've had negative experience in the past with the seals deteriorating if the brake fluid is not changed often enough. In fact, this was from my first Nissan / Datsun, where all the hydraulic seals needed to be replaced when the car was 6-8 years old since the previous owner had never replaced the brake fluid. They said they thought it was coincidental that it started leaking when they did the $1000+ "routine service" back in June, which I accept and agree with. From my past experience, I don't know it there's any way you can easily damage the seals in the purging process, unless they were already 90% of the way to failing, and the pressure applied during bleeding ripped them.

i'd be tempted to try to back the motor off and disable/disconnect it and just use manual force for the brakes. The 17 steps in the removal procedure don't seem anymore complicated than doing a vacuum system M/C replacement.

For now, the brakes feel totally normal, and the only way you'd know there was a problem would be 1) VDC warning light on, and buzzing at startup; 2) No regenerative braking when you push the brake pedal; 3) leaking brake fluid. If I was a big risk taker, I could rebuild the hydraulic seals, and see how it goes, but given the safety risks associated with ignoring it, I wouldn't do it without assurance from someone with knowledge of the car design (e.g., a Nissan rep) that there wouldn't be a future safety implication. I think is almost impossible that I'd get that kind of assurance. I think there's a very good chance that at a minimum, the anti-lock braking wouldn't work, based on other information I've read on what that warning light is telling you. If it was just "no power boost", I'd probably be okay with that, but given the extreme complexity of the system, I don't feel like I really have a strong understanding of all the things it's doing, and which ones will and will not be functional after this failure.

Bob

 

[Nubo]

...They said they thought it was coincidental that it started leaking when they did the $1000+ "routine service" back in June, which I accept and agree with. From my past experience, I don't know it there's any way you can easily damage the seals in the purging process, unless they were already 90% of the way to failing, and the pressure applied during bleeding ripped them. ...

A brake cylinder can develop a "step" where the seals stop travel during normal braking. Then when bleeding, existing wear on the seals can be exacerbated when they run back and forth over the step.

The complexity of this system is one reason I don't begrudge the 2-year brake fluid replacement that's specified, to minimize wear.