Full brake service and fluid flush to Bosch DOT 5.1 - 2018 LEAF SL

I purchased a 2018 LEAF SL about 18 months back from a local driving school that ironically had used the same car to teach my daughter It was a leased car, so I'm pretty sure the brake fluid was never flushed, and I know for sure that the pads/caliper pins had never been serviced. I've been using a Motive pressure bleeder on our other cars, but could not find a cap from them to fit the 2018 (2 prong) LEAF master reservoir. I finally found one reseller "SpeediBleed.com" which stocked a cap for the LEAF (C1000 kit) so ordered this up with a few extra quick release fittings (male 1/8" NPT) to convert my Motive caps over to this system. Motive pressure bleeders need to be pumped up manually, but SpeediBleed includes a fitting to pull pressure from a tire and a regulator to set pressure.

The car was up on the hoist for winter/summer tire swap, so it was a perfect time for brake service. Before doing the brake service on a 2018 LEAF you should turn ePedal option off (so brake pressure is not applied when you park, then turn the car off. Don't apply the ebrake. Wait 3 minutes with everything off, doors closed, then disconnect the 12V battery.

I decided to use BOSCH ES16-N32 DOT 5.1 fluid instead of OEM DOT 3 specifically due to the much lower viscosity of the DOT 5.1 fluid at -40C. We see temps approaching that here in winter. The 670 mm2/2 kinematic viscosity of the BOSCH DOT 5.1 fluid is much less than the the DOT 3 spec at 1500 mm2/s at -40C which means the LEAF electronic braking system should perform much better at very cold temps with the DOT 5.1. I also researched the fluid (actually the US military did) and posted my findings here: https://bobistheoilguy.com/forums/threads/brake-fluid-military-testing-dot-3-v-dot-4-vs-dot-5-1.354498/

Any concerns I had about seals, corrosion, performance etc. went away with the those study results on the DOT 5.1 vs 3. If you did want to stick with DOT 3, then 100% you should use AC DELCO Brake and Clutch Fluid (GM OEM) which has very low cold temp viscosity (much better then the DOT 3 spec) and lower water absorption as well. That fluid is actually made by DOW, DOW 372LB. See the study I linked above on the DOW DOT 3 low viscosity fluid testing results.



I rarely charge to 100% but apparently had turned the charge timer off (it was only supposed to go for four hours) and the car topped itself off. I guess time for a BMS calibration..ha.



This is the SpeediBleed connected with a litre of Bosch 5.1 fluid added to the bottle. I had some air bubbles exiting the pressure bottle due to a tiny split in the pickup tube inside the bottle. I just removed the threaded fitting and swapped the internal fluid pickup tube end to end to resolve this. You should see zero air bubbles in the fluid leaving the pressure bottle! Keep on eye on the fluid level and make sure the master cylinder stays full. Running it dry will cause you major headaches in some cars, like my Audi A3 as I got air in the ABS system. It took 3 hours of repeated bleeding, using a laptop and VAG software to run the ABS bleed sequence.



The Speedibleed comes with a connection to pressurise via a tire, but I removed that and replaced with a standard air fitting so I just use my shop air. The unit comes with a nice little regulator so you can dial in 15 PSI. Going higher is not a good idea with a plastic reservoir!



SpeediBleed sells this slick little adapter (Motive does not) for late model Nissan LEAF (C1000 model cap) and like all their caps incorporates a 1/8" NPT quick release. I ordered some additional male 1/8" NPT fittings to convert my other caps to this unit. The gen 2 (2018 and up) LEAF uses a 2 prong cap, which is not the same cap as a 2011-2017 model.



With pressure on the cap, you just need to go to each corner and let the brake fluid flush via the bleed screw. I use the sequence FL, RR, FR, RL so "old" fluid is flushed out via the shortest path first. With the Speedibleed unit, you just set the air pressure at the regulator and let it go. With the Motive you need to pump it up frequently to build pressure which is a PITA on the hoist.

The OEM DOT 3 (likely 4 years old) tested at around 1% water, and looked a bit cloudy, but not terrible coming out.



Bosch ES16 DOT 5.1 fluid has a yellow tinge, but you can tell it's fresh more or less by how clear it is. I ran about a litre through the system in total.



I used Permatex Silicon/Ceramic (Orange) brake lube on the pins, shims and caliper/brake contact points. The LEAF has never had a proper brake service evidently (it was a leased car previously) as both rear inner pads were pretty stuck and took some tapping and prying to remove them. Same thing with one of the front inner pads. Correct lube and cleaning will prevent this, increase your EV efficiency and improve braking as well. I have not always removed pads during brake service (doing the caliper slide pins yearly) but I will now. The rear brakes on a LEAF don't see much use or heat for that matter...so the pad cleaning/lube part of service becomes even more important.



Torquing the 14mm caliper slide bolts to about 26 ft/lbs will do the trick. You should check the 17mm caliper frame bolts to make sure they are least at 85 ft/lbs. I use anti-seize on both the caliper and frame bolts (we see a lot of winter salt) so back these numbers back a tad as "wet" torque specs are always less. In non corrosive environments you'd likely want to use loctite red on the 17mm frame bolts and blue on the 14mm caliper slide bolts.

If your car has an electronic ebrake (the 2018 LEAF SL has one) then don't try and retract the rear caliper pistons! You'd need to remove the actuator motor from the caliper and wind the ebrake back to do that. There are a few Youtube vids out there on how to do this manually without the OEM software. The OEM software will allow you to wind back the internal ebrake actuator by controlling the ebrake motor from the software which is obviously a bit nicer than removing the ebrake motors

Very helpful -- thanks

I presume people here know that a pressurized system is not required. Just keep DOT3 in the brake fluid reservoir so that air is not introduced while the bleeder valve is draining fluid. The system can be flushed by stepping on the brake pedal repetitively. Take your time and do not be aggressive.

I don't think it is a good idea to mix DOT3 and DOT5.1 so if a change of formulation is desired a very complete flush is needed.

Thanks for the info. I've got the fluid ready but your post reminds me I have never given the 8-yo slidey parts any love so it's time to get some brake lubricant.

Nice write up Denwood , I've been using the vacuum bleed/flush process over the years and this looks slick n quick. And never knew about the 5.0 fluid.

Sage, yes you can do this with one person pressurising at the pedal, and another at the bleed screw, This works well, but you need to coordinate so the bleed screw is only open when the pedal is under pressure, and never open if the pedal is being raised. Otherwise, you'll just suck air. My wife and daughters are not so keen on getting into the car on the hoists, so the pressure system allows me to do this work solo

Nubo, the car sees a lot of salt in winter, and has 62 000 kms. I'm not sure if anyone removed/cleaned/lubed the pads and three were more or less "locked" in position. All three of the problem pads were inboard. If you're servicing the caliper glide pins (which you should do at least yearly), just check and make sure the pads can be moved easily away from the rotor by hand. If not, remove and lube them!

Steel, I have a vacuum bleed system but I always found the pedal a bit soft after, and had to follow up with the two person pressure bleed to finish the job. The issue is that when you loosen the bleed screw and attach a hose to it, air can still enter back into the system (or into your vacuum canister) via the bleed screw threads. If you keep a constant high vacuum and are very careful to close the screw while vacuum is applied, (hard to do with a hose on the nipple) you're likely fine. I just find that for similar cost ($90) a pressure bleed system is faster and pretty much idiot proof...as long as you make sure there is fluid in the bottle. I've never had issues with a firm pedal after using the pressure system to bleed or flush the brakes...so that's why I use it 100% now.

There is another method often referenced on Youtube using a bottle with fluid in it, attached to the bleed screw. This is even worse, as if you're doing it solo via the brake pedal, air can enter every time you release the pedal (via bleed screw threads). If you're using this method, all good...but you need to follow up with the two person pressure bleed method to ensure any air that was sucked in during pedal raise is purged at each caliper.

denwood said:

Sage, yes you can do this with one person pressurising at the pedal, and another at the bleed screw, This works well, but you need to coordinate so the bleed screw is only open when the pedal is under pressure, and never open if the pedal is being raised. Otherwise, you'll just suck air. My wife and daughters are not so keen on getting into the car on the hoists, so the pressure system allows me to do this work solo

Click to expand...

The problem of air getting sucked back into the line can be prevented by putting the 1/4" tube that is in a jar under fluid. I have some old DOT I am keeping around just for that purpose. You also want to keep the bottle above the valve

Sage, this doesn't address the issue of air being sucked back via the bleeder screw threads. The bleed screw seats/seals via a taper at its base, but it has a hole at the base (on the side of the hollow screw). Once you loosen it , there are two paths for air to enter. Path 1 is via the hollow bleed screw, and path 2 is via the bleed screw threads which are not designed to be airtight even when tightened. When you place a tube over the bleed screw (with the end submerged in fluid) you isolate path 1, but not path 2. If using the brake pedal to pump, there is significant suction when the pedal is being raised...and the air may take path 2 as the one of least resistance. That's why pressure bleeding works so well...there is never any suction on the system and therefore no possibility for air to enter.

Any air bubble that makes its way to the ABS system or sits in the caliper will give you a soft pedal, and compromised braking on that wheel...so if using suction or the fluid filled bottle methods, make sure you follow up with a two person pressure bleed (one on the pedal, one on the bleed screw) to ensure all the air is out of the system.

This pic illustrates path 2...and if you're pumping away on the pedal (even with a fluid filled bottle attached) the air can still get sucked back into the caliper via the threads. You can avoid any of this by just using a pressure bleeder

Reference: http://sportsterpedia.com/doku.php/techtalk:ref:wheels06

^^ That makes sense to me -- thanks.
I'll either draft my wife for the finale or jerry-rig a weight to hang on the brake pedal.

I wonder if one could just apply some silicone to the bleeder valve threads before attaching the tubing to ensure a good seal.

Or just have her sit in there for a few minutes as you flush the system. This video details that method:

https://www.youtube.com/watch?v=tl1Q-AhfgjU

@denwood

What setup did you use to collect the old brake fluid? I'm not sure of the hose size that fits the nipple, bottle, etc.

3/16 ID x 5/16 OD vinyl tubing works well. Clear tubing is nice so you can see the fluid inside.

As for the jar, any old bottle works. Plastic is nice so it won't fall and break. Many auto parts stores will recycle the old brake fluid or if you have a household hazardous waste place handy they will take it too.

@trentr, I just use a collection tray under the wheel assembly and wipe up after.

It's been two years now and the Bosch 5.1 fluid has done its job, particularly in very cold temps. Zero issues. I just checked the fluid moisture levels and they did not reqister (so between 0 and 1%) so will do the flush next spring, three years of use.