Power Brakes

[highcountryrider]

I haven't noticed the grabby/numb thing yet. I can feel the transition from regen
to hydraulic, but it's smooth enough for me and not a bother. I do approach stops
gradually, though, and that might make a difference.

I did notice something a day or two ago. I was approaching a stale green light that
turned yellow shortly before I got to the stop line. I judged it safe to nail the brakes
and glanced over at the motor power gauge expecting to see massive regen. I saw
almost nothing. Apparently the hydraulics took over in that hard-stop situation.
There was nothing odd about restarting after, but I don't think I did any creeping.

Looking at the Service Manual, bleeding the LEAF is routine, there is nothing extra to
do for the ABS in the LEAF.

[TomT]

With ABS, it is best to use a power bleeder to insure that all the fluid in the ABS system is exchanged. This is pretty much standard procedure these days for a brake fluid change.

Looking at the Service Manual, bleeding the LEAF is routine, there is nothing extra to
do for the ABS in the LEAF.

[TEG]

I did notice something a day or two ago. I was approaching a stale green light that
turned yellow shortly before I got to the stop line. I judged it safe to nail the brakes
and glanced over at the motor power gauge expecting to see massive regen. I saw
almost nothing. Apparently the hydraulics took over in that hard-stop situation.
There was nothing odd about restarting after, but I don't think I did any creeping.

Just watch the regen gauge as you slow brake towards any stop.
It seems to cut out as you get down to very slow speeds.
There must be a reason they want to switch you over to friction brakes just before you stop.

[AlGrsn]

The Leaf has conventional hydraulic brakes: master cylinder, four calipers and the booster/antilock/traction/stability control unit. This adds push depending on the regeneration, the pressure on the pedal. Rather than a vacuum assist reservoir the Leaf has a capacitor bank to provide emergency power assist.
Because of the lack of “engine braking” comparable to ICEengines with downshiftable transmissions, the Leaf depends more heavily on the integrity of the hydraulic brake system. For this reason the fluid change interval is 2 years (1 year in harsh conditions) rather than 3-5 years for conventional ICE cars. Further, the master cylinder and booster pump are very expensive to replace, so we don't want its life shortened by water contaminated fluid.

[cwerdna]

^^^
Seems like BS to me. My gen 2 Prius which I had for 13 years was just like this w/regen and a capacitor bank in the trunk area.

I don't recall crazy brake fluid change intervals or any at all. If I'd ever had the brake fluid changed, it was probably only once during the time I had the car. Will need to check w/the maintenance guide for my mom's 07 Altima Hybrid (based on Toyota hybrid synergy drive).

I do have a device to measure brake fluid moisture level and test strips to measure copper content. Both were fine on my '13 Leaf when I last checked a few weeks ago.

I suspect the silly brake fluid change intervals + the annual "required" battery check were bones that Nissan corporate threw to dealers to make up for other lost maintenance revenue (oil, spark plug, belt, etc. changes, throttle body and EGR cleaning, etc.)

[LeftieBiker]

I agree on the above about Nissan throwing their dealers some business. As for no engine braking increasing the stress on the brakes, that is more or less true only if you use Normal driving more. If you drive in Eco and/or in B or ePedal mode, you get plenty of regen braking.

[gncndad]

The Leaf has conventional hydraulic brakes: master cylinder, four calipers and the booster/antilock/traction/stability control unit. This adds push depending on the regeneration, the pressure on the pedal. Rather than a vacuum assist reservoir the Leaf has a capacitor bank to provide emergency power assist.
Because of the lack of “engine braking” comparable to ICEengines with downshiftable transmissions, the Leaf depends more heavily on the integrity of the hydraulic brake system. For this reason the fluid change interval is 2 years (1 year in harsh conditions) rather than 3-5 years for conventional ICE cars. Further, the master cylinder and booster pump are very expensive to replace, so we don't want its life shortened by water contaminated fluid.

Isn't regen braking the OPPOSITE of the highlighted phrase??? I thought one of the strongest benefits of regen braking was to reduce the load/stress on the hydraulic system. 2 year fluid change? Maybe, if I lived in high humidity year round. I've settled on 3-4 years for all of my cars (hybrids/elec) precisely because the stress on the fluid is so low, and the humidity in the DFW is higher than I would like, most of the time.

As for pads/rotors, another "HAHA!" My 2014 Avalon pads are at 8mm all around, after 111k miles.

cwerdna: I'm curious about how you test brake fluid with test strips. Do you open the bleed valve and capture fluid at the end of the hydraulic line, or simply dip the test strip in the fluid reservoir? It's my understanding that brake fluid doesn't really circulate (return to the reservoir), so is dipping into the reservoir accurate?

[LeftieBiker]

Because the fluid in the reservoir is exposed to more air, and thus more water than the fluid in the lines, testing the reservoir is fine, because it's testing the "worst" of the fluid.

[gncndad]

Because the fluid in the reservoir is exposed to more air, and thus more water than the fluid in the lines, testing the reservoir is fine, because it's testing the "worst" of the fluid.

I'm not sure I'd agree. I'd think the fluid closest to the heat of the brakes (thermally challenged) would be pretty nasty, as well. I think of the reservoir as simply a holding tank for the system. I'm going to read up on this, because...I'm...OCD!!!

[LeftieBiker]

Go for it! Me too on the OCD. I'm just too tired these days to be good at it.

Look at it this way: sustained extreme heat likely does degrade brake fluid, but an EV like the Leaf sees little of that, relatively speaking. The damp air of a typical Fall or Spring coming into contact with the open reservoir adds water, while heat in the calipers generally doesn't. So it seems to me that the most deteriorated brake fluid would be in the reservoir, not in the lines or calipers.