Synthetic Brake Fluid Myth?

[Pete2k_Z28]

Just a random thought....

Why is it then that brake fluid can be disposed of with standard waste oil when it is not oil based?

Always wondered that but this thread just got me thinking

 

[outrun]

This point has went unanswered throughout the string.

If someone uses a DOT 4 instead of a OEM recommended DOT 3 will SEAL DAMAGE occur?

The reason why i ask is that i my requires DOT 3. I once added Valvoline SynPower to the system 3 years ago...but it has been flushed once since then.

A year and a half ago my front PBR caliper seals were eaten away.

Was this routin wear and tear or did SynPower eat the seal-gasket material.

Now im afraid, unless i recieve credible word otherwise its standard OEM in a can DOT 3 fluid

 

[moribundman]

I'm not sure if this will answer your question, but the Valvoline brake fluid I'm using is DOT 3 and DOT 4 approved.

 

[QuadDriver]

Correct me if I am wrong, but 'wet' in the DOT spec for brake fluid just means it has absorbed water (since dot 3/4 is glycol based, that makes it anhydrous(sp? right word?) no?)

I beleive you can always put dot 4 in a dot 3 application, but not the other way around, whatever needed dot 4 needed the higher bp.

be interesting to see a poll if anyone ever flushes their brake lines out?

 

[VaderSS]

Wet boiling point is the boiling point when saturated with water.

Some manufacturers call for DOT 3 and specifically recommend against DOT 4. I've heard that it is because DOT4 is more hygroscopic than DOT 3.

The ABS actuator on my car lists for $1700 and is available with a discount for $1200.


For that reason, I feel an annual brake fluid flush is cheap insurance.

I don't know if it is possible to access posts once they go away(moderators?), but this was the best discussion on the subject of brake fluid that I have seen.

http://theoildrop.server101.com/ubb/ultimatebb.php?ubb=get_topic;f=1;t=000218#000000

Sadly, I did not save it...

 

[W8liftr]

quote:

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Originally posted by VaderSS:
Some manufacturers call for DOT 3 and specifically recommend against DOT 4. I've heard that it is because DOT4 is more hygroscopic than DOT 3.

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That's interesting. Everything I've read about ATE Super Blue/TYP 200 (which I'll be using) indicates that it's less hygroscopic than DOT 3.

 

[moribundman]

quote:

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Correct me if I am wrong, but 'wet' in the DOT spec for brake fluid just means it has absorbed water (since dot 3/4 is glycol based, that makes it anhydrous(sp? right word?) no?)

I beleive you can always put dot 4 in a dot 3 application, but not the other way around, whatever needed dot 4 needed the higher bp.

be interesting to see a poll if anyone ever flushes their brake lines out?

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QuadDriver,

My Audi requires DOT4. I use Valvoline brake fluid that states right on the bottle that it's safe for brake systems that require either DOT 3 or DOT 4. DOT 4 is less hygroscopic than DOT 3, if I remember correctly. The Valvoline seems to meet DOT 4, but also DOT 3 specs. I'm sure there's a datasheet.
I always flush my brake lines every two years. The problem is the ABS control unit, which needs to be cycled to get all the fluid out, and this requires a computer tool. That's why I have that done at the dealer. Ideally, they should also bleed the clutch master cylinder, since on my car the clutch and the brake share the same system.

[ July 16, 2003, 04:06 PM: Message edited by: moribundman ]

 

[MolaKule]

DOT 4/3/5.1 brake fluids are actually synthetic esters of PEG's or polyethylene glycol ethers, and are a class of synthesized hydrocarbons unto themselves. They have an "ether-like" or alcohol smell like no other fluid, and are hygroscopic, that is, they easily take up moisture, which is why they are contained in a semi-sealed braking system.

The DOT 5 fluids are silcone-based and similar in composition to the anti-fomant additive in motor oils.

The silicone-based fluids (DOT 5), as others have pointed out, are NOT compatible with the PEG fluids (DOT 3/4/5.1).