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Re: Brake Fluid DOT 3 [Re: painfx] #5118940 05/29/19 06:41 AM
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ragtoplvr Offline
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There are small amounts of additives in brakefluid to provide corrosion immunity and lubrication

So if you seldom change it they might make a difference. If you change every 2 or 3 years. no difference.

Rod

Re: Brake Fluid DOT 3 [Re: painfx] #5118946 05/29/19 06:49 AM
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doitmyself Offline
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I wish we could end the confusion surrounding DOT 3 vs. DOT 4. If you Google the subject, the explanations are all over the place.

Things I have read:

- DOT 4 absorbs water slower or faster vs. DOT 3?
- One is better in wet/humid conditions vs. the other?? Either is listed better in different articles.
- DOT 4 should be replaced more often for numerous reasons?
- DOT 4 is more resistant to water absorption, but its boiling point drops of faster when it does absorb water vs. DOT 3. I.E., DOT 4 starts our with higher boiling points, but could drop below DOT 3 specs faster IF it takes on water.
- Borates in DOT 4 "might" damage some systems designed for DOT 3?

From this article: https://www.aa1car.com/library/bfluid.htm
DOT 3 vs. DOT 4
"DOT 4 fluid, which has a higher minimum boiling temperature requirement (446 degrees F dry and 311 degrees wet) soaks up moisture at a slower rate but suffers an even sharper drop in boiling temperature as moisture accumulates. Three percent water will lower the boiling point as much as 50%!"


My take on all of this is that "bigger is not always better". Many people think that DOT 4 is inherently better in all aspects. DOT 3 is still recommended in many OEM manuals. IF your conditions create higher braking heat than "normal" , then choose DOt 4. If you live in the flatlands and drive like Grandma Moses, the benefits of DOT 4 will never be realized. And, if my quote above is accurate, the DOT 4 might be worse if you neglect maintenance.

Re: Brake Fluid DOT 3 [Re: painfx] #5118951 05/29/19 06:57 AM
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JLawrence08648 Offline
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I change mine every 30,000 miles, though it is a complete brake flush, I'm surprised as the car gets older, the brake fluid gets darker meaning it's rusting internally.

I use only synthetic brake fluid with the maybe false assumption that synthetic brake fluid absorbs less moisture.

Re: Brake Fluid DOT 3 [Re: painfx] #5118970 05/29/19 07:19 AM
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StevieC Offline
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I change brake fluid every 2 years regardless of mileage because it likes to absorb moisture. Have never had a caliper, wheel cylinder seize up or abs distribution module go bad and no brake lines replaced. The fluid always comes out clean instead of rusty.

I use any shelf oil that is a major brand. I also look at the dates and try to source the freshest I can. I store remaining fluid inside tightly sealed and will not use it again if it sits in this condition more than 6 months.

Last edited by StevieC; 05/29/19 07:19 AM.

'18 Caravan - 48k KM - AMSOIL SS 0w20, Fram Ultra, TC-W3 500:1
'06 Santa Fe - 535k KM (Retired)

There is no such thing as "lifetime" fluids! mad
Re: Brake Fluid DOT 3 [Re: painfx] #5119023 05/29/19 08:14 AM
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Snagglefoot Offline
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I had a buddy who was a car nut. I asked him how often he changed his brake fluid. He said " Never. Do you think that's often enough?" laugh

Last edited by Snagglefoot; 05/29/19 08:15 AM.

If you want the job done right......do it yourself.
Re: Brake Fluid DOT 3 [Re: JLawrence08648] #5119072 05/29/19 09:04 AM
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atikovi Offline
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Originally Posted by JLawrence08648
I use only synthetic brake fluid with the maybe false assumption that synthetic brake fluid absorbs less moisture.


Umm, ALL brake fluid is synthetic.

Re: Brake Fluid DOT 3 [Re: painfx] #5119125 05/29/19 10:00 AM
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painfx Offline OP
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I heard that DOT 4 is not always a compatible/universal for DOT 3.

I do know that all brake fluids are synthetic. But not all oils are created the same.

Brake fluid from the master cylinder recirculate to the entire system right? So if I suck the old fluid and put in the new, wouldnt that help extend the time to flush out the brakes?

Re: Brake Fluid DOT 3 [Re: painfx] #5119236 05/29/19 11:21 AM
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atikovi Offline
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No, brake fluid doesn't circulate in the system. When you step on the brake you're pressing on a column of fluid. The chances of the new fluid in the MC reaching the nearest caliper, letalone a rear one is slim.

Re: Brake Fluid DOT 3 [Re: doitmyself] #5119283 05/29/19 12:22 PM
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AC1DD Offline
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Originally Posted by doitmyself

- Borates in DOT 4 "might" damage some systems designed for DOT 3?



VERY important technical factor especially in older Japanese cars from the mid 90s and prior!

[USE ONLY DOT 3 IN THOSE VEHICLES WHEN THE MANUAL SPECIFICALLY CALLS FOR DOT 3!!!!!

Using DOT 4 may destroy the rubber seals which were NOT DESIGNED to be subject to Borates.

Re: Brake Fluid DOT 3 [Re: AC1DD] #5119297 05/29/19 12:38 PM
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kschachn Offline
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Originally Posted by AC1DD
VERY important technical factor especially in older Japanese cars from the mid 90s and prior!

USE ONLY DOT 3 IN THOSE VEHICLES WHEN THE MANUAL SPECIFICALLY CALLS FOR DOT 3!!!!!

Using DOT 4 may destroy the rubber seals which were NOT DESIGNED to be subject to Borates.

Any technical information to support that statement? I've been using DOT 4 fluid in my 1996 Accord for years, no problems yet.

Seems like if that was a "thing" it would say so on the container, rather than saying it is completely compatible with DOT 3.


1994 BMW 530i, 251K
1996 Honda Accord, 280K
1999 Toyota Sienna, 430K
2000 Toyota ECHO, 284K
Re: Brake Fluid DOT 3 [Re: painfx] #5119310 05/29/19 12:54 PM
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While DOT fluids are all government specs, I've read the fluids CCI supplies to the Japanese OEMs(and available at their dealerships) is slightly more lubricating. Toyota and Honda had a recall years ago with some Aisin master cylinders having leaky seals - the TSB noted that aftermarket fluids can exacerbate the issue.

Re: Brake Fluid DOT 3 [Re: painfx] #5119390 05/29/19 02:35 PM
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hallstevenson Offline
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Originally Posted by painfx
How often should one change the brake fluid?
Some automakers don't mention changing/replacing/flushing brake fluid. Ford, for instance, at least what I was able to find or not find. Honda, on the other hand, says every 24 (or is it 36 ?) months. Mileage isn't a factor to them.

Originally Posted by painfx
Can just sucking the old brake fluid from the reservior every few thousand miles be good?
If you don't want to go too in-depth (or pay a shop) - a local shop quoted me $80 to do this - just put a piece of tubing on the bleeder screw and crack it open and let it gravity-bleed for a while.

Re: Brake Fluid DOT 3 [Re: CT8] #5119393 05/29/19 02:38 PM
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Originally Posted by CT8
Siphoning out the M/C does not really do any good
I've wondered how much, if any, does brake fluid "circulate" or is it somewhat static ? For instance, if a piece of "dirt" fell in the master cylinder, will it eventually make it to one of the calipers, then to another, and so on ?

Re: Brake Fluid DOT 3 [Re: hallstevenson] #5119414 05/29/19 03:10 PM
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AC1DD Offline
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Originally Posted by hallstevenson
Originally Posted by CT8
Siphoning out the M/C does not really do any good
I've wondered how much, if any, does brake fluid "circulate" or is it somewhat static ? For instance, if a piece of "dirt" fell in the master cylinder, will it eventually make it to one of the calipers, then to another, and so on ?


Someone here discussed that some time ago...I believe they said that the fluid at the front calipers/piston areas was BLACK as night even after doing the refreshing the fluid with the turkey baster out of the MC reservoir.

Re: Brake Fluid DOT 3 [Re: JLawrence08648] #5119431 05/29/19 03:21 PM
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edyvw Offline
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Originally Posted by JLawrence08648
I change mine every 30,000 miles, though it is a complete brake flush, I'm surprised as the car gets older, the brake fluid gets darker meaning it's rusting internally.

I use only synthetic brake fluid with the maybe false assumption that synthetic brake fluid absorbs less moisture.

Brake fluid change interval should be based on time.
I change every 2 years, regardless of milage.


11' BMW 328i xDrive 6MT (BMW TPT 5W30+OE filter)
11' VW Tiguan 2.0T (Castrol 0W30+OE filter)
15' Toyota Sienna AWD (Mobil1 5W30 EP+OEM filter).
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