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PostPosted: Sun Jan 02, 2011 11:56 pm 
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Location: Foothills of Granada Hills, CA
Delivery Date: 01 Mar 2011
Leaf Number: 000360
Yep, both my BMW and Acura recommend a change every three years for this exact reason.

Gonewild wrote:
These chemicals are hygroscopic, that is they have a tendency to absorb moisture.

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PostPosted: Mon Jan 03, 2011 11:10 am 
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mogur wrote:
Yep, both my BMW and Acura recommend a change every three years for this exact reason.

Gonewild wrote:
These chemicals are hygroscopic, that is they have a tendency to absorb moisture.

Exactly!

This has nothing to do with the Leaf being an EV and has everything to do with keeping the system operating for the long haul.

Brake fluids are a type of hydraulic fluid. They must transfer the force from the pedal to the wheels. They must also protect the metal and rubber parts, lubricate, remove heat from the wheel cylinders, release air bubbles without foaming, handle some water - and keep it from reducing performance or damaging parts. The additives are depleted as they are used, and the brake fluid can only hold so much water before it's saturated.

The brake system is not sealed. Any system that heats some during the day and cools at night (brake system, fuel tank, crankcase, oil drum, etc.) will 'breath'. Daytime heating causes air to expand and the container 'exhales'. Night time cooling causes the air inside the container to contract and the container 'inhales'. The inhalation brings in moisture (humidity is higher at night) and can bring in other contaminants. It doesn't matter if it's an EV or ICE, and doesn't matter if the car's driven or sitting in a barn.

That's how the water gets in...then what?

Most brake fluids are alcohol based (the DOT 5 fluids are silicone based but not generally used in passenger cars). Alcohol 'binds' water - the water is absorbed into the brake fluid solution. Eventually, the fluid can't hold any more water and it stays in the system as a liquid. Fluid with water has a lower boiling point - and water's boiling point is lower still. Boiling makes steam, steam compresses - it cannot transfer power. Water is more dense than alcohol - and the water settles to the lowest parts of the brake system - the wheel cylinders where it causes rust and deposits to form. Water is not a good lubricant. The wheel cylinders use a rubber 'piston ring' to keep fluid inside and the rubber is damaged when it's dragged past the rusted/pitted wheel cylinder.

The rubber seals in the master cylinder and brake cylinders wear and leave particles in the fluid. There can be metal wear particles and dirt as well - air is dirty and the brake system doesn't have an air filter. Toss in crud, water, and heat and then rust particles and the brake cylinders become a muddy mess.

Per the Nissan service manual, there's nothing special about bleeding the brakes on the Leaf - any shop or even owner can do it.

http://en.wikipedia.org/wiki/Hydraulic_fluid
http://www.mightyautoparts.com/pdf/articles/tt136.pdf
http://www.ehow.com/facts_7429801_brake-fluid-problems.html

It's a LOT less expensive to change $4 worth of brake fluid every couple of years than to change a single wheel cylinder.


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PostPosted: Mon Jan 03, 2011 1:30 pm 
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Location: Vallejo, CA
Delivery Date: 0-12-2011
Leaf Number: 16000
garygid wrote:
...Is there no "superior" brake fluid that does NOT attract water?


Yes, DOT 5 brake fluid. Unfortunately not compatible with ABS

http://en.wikipedia.org/wiki/DOT_5

Brake fluid flush should be periodic maintenance on most cars but is widely ignored.

Flush the fluid on a 5-year old car that has never had it done. Collect the old fluid in a glass jar and it will be immediately apparent why this is important.

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Last edited by Nubo on Mon Jan 03, 2011 1:36 pm, edited 1 time in total.

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PostPosted: Mon Jan 03, 2011 1:32 pm 
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Location: Vallejo, CA
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AndyH wrote:

...
The service manual shows the process - and it's a very simple bleed process that can be done with one technician and a vacuum pump (MityVac type device) or two people with one pushing the brake pedal and the second moving from corner to corner.



Also, one-person operation with "Speedbleeders"

http://www.speedbleeder.com/

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PostPosted: Mon Jan 03, 2011 2:25 pm 
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prberg wrote:
Will skipping the brake fluid change void our warranties? I would understand if the brakes stopped working they could point to the brake fluid not being changed, but could they void the entire warranty (and also the battery warranty) if we skipped the fluid change (or did it less often then they recommend)?

-Peter


There isn't a single warranty, there's basically a separate warranty for every part that eventually goes back to the part manufacturer. Nissan acts as a 'warranty agent' so we don't have to go back to the brake pad manufacturer or the company that made the radio buttons. The US warranty consumer protections make sure that if we fail to change the brake fluid then the only warranty that can be affected is parts touching the fluid or that can be damaged as a result of the bad fluid - and then the burden of proof is still on the manufacturer. What 'might' happen is not for debate - it's what actually happened.

Now, if there was a defect in a brake that resulted in a crash, Nissan would be on the hook for the brake problem and all the resulting damage. If we didn't change the fluid, and the resultant weak brake performance caused the crash, I'm thinking we're on our own. ;)

I guess we either change the brake fluid every 12-24 months to maintain their warranty, or we choose to self-insure at the 24 month+1 day point. ;)

My friend the ASE tech is in the business of recognizing when something's broken and replacing it. I'm in the business as a lube tech and reliability professional of keeping things from breaking as long as possible. ;)


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PostPosted: Thu Jan 13, 2011 1:55 pm 
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I know that in one EV I build I used a high performance synthetic gear oil that was low friction and gave improvements in efficiency over standard gear oils. I can't remember the brand but many EV builders use it.

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PostPosted: Thu Jan 13, 2011 2:07 pm 
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EVDRIVER wrote:
I know that in one EV I build I used a high performance synthetic gear oil that was low friction and gave improvements in efficiency over standard gear oils. I can't remember the brand but many EV builders use it.


The Leaf uses synthetic automatic transmission fluid - Nissan Matic Fluid S. Any lower viscosity and it would be water. ;)

I'm glad Nissan chose a common fluid. The Ranger uses a specialty single-source fluid from a company that stopped making it a year ago. I'm glad Nissan designed the gearbox to be on the road and serviceable for a bit longer than 10 years!


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PostPosted: Mon Jan 31, 2011 2:52 pm 
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mogur wrote:
Where can one even FIND an oil that doesn't meet SG/SH specs these days (which is what the vast majority of manufacturers specify)? A couple of cheap straight grade oils in the bargain bin at Pep Boys maybe?

AndyH wrote:
Provided that one uses oil that meets or exceeds the manufacturer recommendations then yes - absolutely! The problem is that 1. most people don't

http://www.imakenews.com/lng/e_article000346479.cfm?x=b11,0,w
Quote:
An alliance of international auto manufacturers says it has concrete evidence that API category SA engine oils -- long obsolete but still widely sold -- are "likely to cause serious damage" and lead to increased emissions if used in engines built since the 1940s. And now it wants the American Petroleum Institute, SAE International and other lubricant industry organizations to help educate consumers not to use such products, which typically lack engine-protecting additives.


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PostPosted: Thu Mar 03, 2011 5:39 pm 
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pretty much all is said about brake fluid, wtih one thing - unless you are racing - you won't loose your brakes due to old fluid. You can run junkies on original fluid from 1980.

BUT you'll be changing pads and rotors more often, as pistons start to get corrosion from water that's now in brake fluid, and won't retract fully. They will still work, but will add drag. I wouldn't want this on Leaf. And if you replace pistons along with brake pads and rotors on your car - you don't have to worry about brake fluid change.


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PostPosted: Thu Mar 03, 2011 7:02 pm 
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Location: Boca Raton FL
Delivery Date: 10 Dec 2011
Leaf Number: 5926
Funny how people are easily persuaded to change engine oil every 3000 miles, even though the mfr says once a year or whatever is enough, but they're content to totally neglect other fluids. Case in point is transmission fluid. Transmission costs nearly as much or more than the engine, and sure there's no blowby gasses polluting it, but do you really want 8 year old rancid gook running through its veins?

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