@ Molakule......differences in DOT 3 & 4 chemistry

[antiqueshell]

There is another thread here concerning the differences
between DOT 3 and DOT 4. However I think something that is being ignored in the different chemistry that is used in different brands and each spec as well.

One of the most critical issues is that I have heard even here on
BITOG that certain chemicals used in DOT 4 spec brake fluid
can actually be very damaging to certain rubber seals that are
used in systems that use DOT 3 fluid.

So Molakule is it true that certain chemicals used in certain
brake fluids can potentially damage certain seals and rubber.
I wish I remembered the chemical that someone specifically pointed out and potentially corrosive to rubber seals.

SODIUM HYDROXIDE is the name of this chemical...What can you tell us about this chemical and whether or not it poses a potential
problem with the brake systems on that use or specify DOT 3?

 

[Rolla07]

Dot 3 and 4 are interchangeable but not Dot 5. Are u aure you are not mixed up?

 

[antiqueshell]

Originally Posted By: Rolla07
Dot 3 and 4 are interchangeable but not Dot 5. Are u aure you are not mixed up?


But different manufacturers do use different additive chemicals in their products whether DOT 3 or DOT 4. As long as they meet the
specs by the DOT. I have a question as to the issue with the chemical I mention above, which is NOT used in all brake fluid products that are either DOT 3 or DOT 4.

 

[brandini]

3 doesn't have esters
4 does
at your own risk for seal compatibility
also have different viscosity requirements so those with ABS, traction control, stability control, electronic brakeforce distribution should try and stick with what's recommended

 

[loubapache]

Originally Posted By: brandini
3 doesn't have esters
4 does
at your own risk for seal compatibility


OK. Then how about this?

Valvoline® DOT 3 & 4 Brake Fluid

For all ABS, drum or disc brake systems requiring DOT 3 or DOT 4 fluid
Compatible with all braking systems requiring a DOT 3 or DOT 4 fluid

 

[brandini]

Likely they made a 4 without esters that's still under the viscosity maximums of DOT3 thus a dual-spec fluid. But they state such by putting it on the label, not true for something simply labeled DOT4.

 

[chrisri]

It's interesting that DOT3 brake fluid was phased out in Europe in late 80s/ early 90s due to its lower boiling point compared to a DOT4.
I have used DOT4 in many 80s cars without any issue. So did others too because DOT3 is not readily available any more.
Only issue I can remember with brake fluid is when some guy poured DOT fluid in a 60s Austin Mini. Master cylinder actually seized because rubber seals blowed.

 

[SHOZ]

Sodium Hydroxide is lye. May be used as a pH modifier.

 

[nthach]

I've used Castrol GT LMA/ATE Type 200 or Super Blue/Pentosin Super DOT4 in my cars and Toyota recommends their fluid - but their marketing says their DOT3 has borate esters to reduce corrosion - so does the German stuff. Should I keep on doing what I'm doing?

 

[MolaKule]

Quote:
One of the most critical issues is that I have heard even here on
BITOG that certain chemicals used in DOT 4 spec brake fluid
can actually be very damaging to certain rubber seals that are
used in systems that use DOT 3 fluid.

So Molakule is it true that certain chemicals used in certain
brake fluids can potentially damage certain seals and rubber.
I wish I remembered the chemical that someone specifically pointed out and potentially corrosive to rubber seals.

SODIUM HYDROXIDE is the name of this chemical...What can you tell us about this chemical and whether or not it poses a potential
problem with the brake systems on that use or specify DOT 3?


Yes, sodium hydroxide is a pH adjuster. Any fluid or chemical compound in a BF is balanced for proper performance.

What chemicals in any properly formulated DOT3,4 or 5.1 BFs that are harmful to elastomeric materials?

Can you please point to any studies or definitive cause-and-effect situations?

I have seen situations in which an uninformed person put Dot5.0 silicon-based BF in the vehicle and totally messed up his ABS brake system, which included a complete ABS controller/pump and seal replacement.

 

[dailydriver]

I know that the top AP Racing fluid does NOT 'play well' with ANY other DOT 4 fluids, and the label states so very clearly.

There might be one or two other pure racing DOT 4s like this as well.