Gentleman

Does anyone know if Toyota Motor Company approves use of DOT 5 synthetic brake fluid for production models manufactured the past 10 years?

<96 Runner>

Nope, not a good idea.

http://www.gadgetonline.com/BrakeFlush.htm

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Mike Murrell

Good post by 96 Runner.

The owners manual in my 2004 Tacoma calls for Dot-3. You could run Dot-4 and raise the boiling point, but definitely stay away from the Dot-5.

foxtrapper

You're asking three different questions.

Dot-5 simply refers to the boiling point temperature. Has nothing to do with being silicone or not.

All brake fluids are synthetic, with the exception of castor oil.

Silicone fluid is compressable, foams, is not compatable with glycol ether brake fluids, and is not compatable with anti-lock servos.

Silicone fluid has a high boiling temperature, and is the typical fluid used in DOT-5 labeled containers of brake fluid, but not always. Racing grade DOT-5 fluids are not silicone.

Silicone ethers are different from silicone fluids. This is the one that is more typically labeled DOT-5.1. It does not foam, is compatable with glycol ethers (though not recomended), and probably can work with an anti-lock servo (not certain of that).

<96 Runner>

OK, so gadget is wrong - that's what you are saying...

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foxtrapper

Settle down. I just gave a bit of information.

<96 Runner>

You still haven't answered my question, and I am far from upset. Just curious.

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foxtrapper

Christian,

You never have asked a question. You just wrote that I said Gadget is wrong. But I'll take a guess at what you're after, namely DOT 5 and silicone brake fluids.

Like I already said, DOT5 is a boiling point. SAE test specifications for DOT5 fluid require the fluid to not boil until 500 degrees when dry, and 350 when wet. Any fluid achieving or exceeding that value can correctly be labeled DOT5. There's a number of other requirements of a DOT5 specification, but that's the important part for this thread.

Currently, the only brake fluids commonly available at automotive stores that meet the DOT5 boil points are silicone. This silicone fluid is cheap to make and as such is marketed as DOT5 brake fluid. Hence the natural mistake of equating DOT5 with silicone brake fluid.

Go over to the racing side, and you will come across non silicone DOT5 brake fluids, as well as different types of silicone DOT5 and higher brake fluids. Due to the racing nature of the application there generally isn't much concern with meeting the dye color specifications of DOT5 (must be dyed light purple), so it is up to the reader to figure out what they are looking at. NEO610 is a handy example of this.

So in quick summary:
1) DOT5 is a test specification.
2) Silicone fluids meet these test specifications.
3) DOT5 does not specify the fluid be silicone.
4) Fluids other then silicone can meet the test specifications.
5) All the DOT5 fluids you find at Walmart will be silicone.

<96 Runner>

OK, I forgot the question mark...

My intention of posting this "question" is so I can clear things up for those of us that do not have degree's in Chemical Engineering. We all know that gadget knows his stuff, and that he is a trusted source for all 3rd gen maintenance and performance parts.

So you reply to the thread with seemingly contradictory information to gadget's...which leads me to probe further.

You sound like you know what you are talking about, unless you copy and pasted, which I doubt you did.

Clarification of the information that seems contradictory is my only motive. That and the fact that I need to change out my brake fluid soon.

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obxfishn

Looks like a question to me........

foxtrapper

Christian,

Maybe I'm being over prickly today. It's not my intention. Gadget has a lot on that web page, and I am in strong agreement with him on the methods to bleed brakes and the importance of flushing brakes. The DOT5 fluid bit is a minor point, and honestly isn't one I even knew until very recently. I do not claim a 100% total knowledge of the subject, and haven't finished reading the SAE specifications on it.

Flush your brakes, don't run DOT5 in abs vehicles, and have a good time stopping well.

<96 Runner>

Dot 4 it is.

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Mystickal

Ummm, not quite. DOT5 is a Department of Transportation Specification (hence the DOT designation) that is spelled out in the Federal Code (it's not just a good idea - it's the law :cry: )

The specifics are in Title 49, Volume 5, Chapter 5, part 571.116 Standard No. 116; Motor Vehicle Brake Fluids. Part 571 is Federal Motor Vehicle Safety Standards - there's a ton of other intersting stuff in there, but for brake fluids, we're interested in 571.116 alone.

That section dicates that DOT 3, DOT 4, and DOT 5.1 non-SBBF shall be colorless to amber, DOT 5 SBBF shall be purple, and hydraulic system mineral oil be green (section 5.2)

It also dicates that brake packaging will be marked with the grade (DOT 3, DOT 4, DOT 5) of the brake fluid, and that DOT 5 shall be further distinguised as "DOT 5 SILICONE BASE" or "DOT 5.1 NON-SILICONE BASE" (section 5.2.2.1(b))

So, while you are correct in that DOT 5 is a test specification, fluids that are MARKED as DOT 5 are required by law to be silicone based, and fluids that meet the DOT 5 spec but are not silicone based are required by law to be marked DOT 5.1.

For those interested in more reading,

From the Federal Code

So, in summary, while DOT 5 IS a test specification, it is also a designator that the brake fluid is silicone based.

~Bill

Mystickal

Forgot to add this to my earlier post -

The test specifications required for DOT 3, 4, and 5 are also listed in there.

~Bill

foxtrapper

Thanks for the link Bill! That gives me a much better understanding of the 5.1 fluid, and I see where I've gotten confused, and have some semi-bad information regarding the split between 5 and 5.1 fluid.

Surprised how recently this standard was updated. Would also explain why I wasn't finding what I was looking for in the SAE manuals.

Thanks again.