Brake Fluid DOT 3

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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.
 
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?
 
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.
 
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.
 
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.
 
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.
 
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.
 
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 ?
 
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.
 
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.
 
Originally Posted by painfx
Who makes the Toyota DOT 3 Brake Fluid?

What is a good brand for DOT 3 brake fluid?

How often should one change the brake fluid?

Can just sucking the old brake fluid from the reservior every few thousand miles be good?

Thanks


What does the owner's manual say in the maintenance section in regards to Brake Fluid change/Flush?

Sucking out the old fluid from the reservoir doesn't cut it. New fluid needs to be flushed through the lines with either:
-a person helping you out pumping the brake pedal while you're observing the caliper bleeder for the old stuff to be flushed out and new stuff coming through
-use a pressure bleeder in lieu of pumping the brake pedal.
 
Originally Posted by maxdustington
Could this be why DOT 3 is still on the shelves when DOT 4 is superior is on the shelf right beside it?

Castrol LMA DOT 4 claims better resistance to moisture - Low Moisture Activity, I believe is what it stands for.
 
Originally Posted by AC1DD
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.


I asked because if you can see the dirty brake fluid from the master cylinder, it has to circulate for it to have dirty fluid right?
 
Ok, I'll try to help sort some of this out:

Dot 4 has a higher boiling point than dot 3, which is better. The higher the boiling point the lower the chance of high temp brake failure.

The more moisture content in the fluid, the lower the boiling point, which is bad.

Brake fluid is supposed to absorb moisture so that the calipers don't freeze.

While brake fluid and the rust/dirt it carries do not circulate in the system, the moisture does migrate through the system. So changing out the reservoir fluid with a turkey baster will reduce your system moisture content.
 
Originally Posted by Kage860
Ok, I'll try to help sort some of this out:

Dot 4 has a higher boiling point than dot 3, which is better. The higher the boiling point the lower the chance of high temp brake failure.

The more moisture content in the fluid, the lower the boiling point, which is bad.

Brake fluid is supposed to absorb moisture so that the calipers don't freeze.

While brake fluid and the rust/dirt it carries do not circulate in the system, the moisture does migrate through the system. So changing out the reservoir fluid with a turkey baster will reduce your system moisture content.


Make sense.
smile.gif
 
Just go with DOT 5.1 and forget it. It has wet boiling temp about same as DOT 3 for dry and highest for either 3 or 4 wet or dry.
Just don't get DOT 5 if yours calls for 3 or 4.
DOT 5.1 isn't that expensive anymore, full bleed may cost you $10 in fluid if you buy it on Amazon or so in 1L bottles.
 
Last edited:
Originally Posted by Kage860
While brake fluid and the rust/dirt it carries do not circulate in the system, the moisture does migrate through the system. So changing out the reservoir fluid with a turkey baster will reduce your system moisture content.

I actually have to believe the fluid does circulate throughout. Maybe not a lot but where does the "dirt" you frequently see in the master cylinder come from ? I believe most of it will be rubber particles and where is there rubber in the brake system ? The majority is at the calipers or just before them. The other parts of the system are some type of metal (brake lines).
 
Originally Posted by AC1DD
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.


This is totally contrary to every DOT 3 and DOT 4 spec I have read. Everything says DOT 3 and DOT4 are 100% compatible, and that DOT 4 can be used anywhere DOT 3 is specified.

Can you show any articles or specifications that say DOT 4 shouldn't be used in any particular application where DOT 3 is specified?
 
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