OK, I will be doing a complete brake swap soon (hoses, calipers, pads, rotors), and as part of that I will be doing a complete fluid flush and refill. Now, is Honda DOT3 brake fluid really any different than "normal" DOT3 brake fluid?

I have had great results with the Motor Medic brand of "heavy duty" DOT3 fluid (has a higher dry and wet boiling point than most others) when I did the same brake rebuild on my 1996 Ford Explorer. After almost 2 years the pads are gone (stupid me, I put truck/tow pads on an Explorer and after less than 10k miles the pads need to be redone, so I am going with the Powerstop Z23 pads on that now), but the brake fluid is in perfect condition. No discoloration or anything else.

In the past I was a big fan of Valvoline DOT3 synthetic brake fluid, but every single car I used it on had the fluid in the master cylinder turn black within 6-8 months because of how aggressive it is to the seals in the master cylinder.

I know ACDelco DOT3 doesn't cause that kind of discoloration, and from what I can tell on the Acura TL, that is not the case with the Honda DOT3 as well.

Now, per someone else they mentioned they prefer the discoloration of the Valvoline since when you go to flush the system you can tell "good" from "bad" at that point as when you bleed you can bleed until it becomes clear. Personally, I would rather not have such a reaction with the seals and prefer the fluid to remain "clear" as long as possible. I know that opening a brake system master cylinder to check the fluid is the way to contaminate it (moisture absorption), and I only do a flush when I need to redo brake pads. I don't ever pop the top of the master cylinder unless I get a low-fluid light (all of my cars have sensors to tell that), and I know DOT3 fluid attracts less moisture than DOT4, thus I have no interest in going to DOT4 (I do run DOT4 on my high-powered sports cars, but they get pads much more often and fluid changes as well).

So, back to the topic at hand, is Honda DOT3 fluid that much "better" than a good quality DOT3?

 

no.

i use autozone dot 3 brake fluid in my 2006 Acura TL.

also, brake fluid is inherently hygroscopic, meaning it naturally absorbs water from the atmosphere...with or without you opening up the master cylinder cap

 

I understand that, but in a sealed system the only way for moisture to get in is via the hoses, seals and the biggest source, the master cylinder being opened to the atmosphere to check the fluid level. (point being that a sealed system is just that "sealed).

The rest (hoses, seals) are really only a concern as a source of moisture after about 15+ years. The fact is the majority of moisture that gets into the brake system is via the master cylinder and the airspace it naturally has. Beyond that there is very low permeation via the hoses and seals. Honestly, the biggest concern is for collectors and cars that are used infrequently enough to reach a point where the fluid should be changed out because it has sat too long.

Being an engineer myself I have read all of the papers on that stuff. I just didn't know if the Acura/Honda fluid had anything "special" about it in regards to compatibility of the formulation with internals of the system. If it is all DOT3 "generic" then so be it I will continue to use what I plan on using.

Seriously, the big issue with moisture after manufacture is the fact that people are flushing the system too often. Too much moisture can be built up and the only way to remove it all is to rebuild the calipers, master cylinder, replace the hoses and flush the lines (and ABS unit) as much as possible. Best would be to even replace the hard lines. Contaminated fluid (ie, fluid with too much moisture) that coats the internals is the big issue, since it is impossible to get it all out.

That is why they recommend a fluid replacement after so many years and the frequency of the fluid replacements get much more aggressive after that.

But, if you redo the entire brake system, like I am, then you fall back to a setup where less frequent fluid changes are "recommended".

Honestly, I can say that people are probably too aggressive in brake fluid changes. Unless you boil the fluid, and as long as you don't constantly open the master cylinder, you are good for a very long time, at least 5-7 years. Some cars that have had hydroscopic analysis done of the brake fluid after 10 years (low-usage vehicles) are found to have perfectly fine brake fluid with very very low moisture absorption. Of course if you are putting 15k-30k miles on a car in a year (or more) you are going through brakes at a much more accelerated rate and changes need to happen more frequently.

A LOT of the paranoia of fluid changes for brakes (and coolant for that matter) is because of the dealerships wanting to make more money with services. In severe usage you can make a case for it, but for regular commuter use, it just doesn't make sense.

 

was just answering your question about generic dot 3

but no, i dont think people over change the fluid....in all my 12 years of working on cars, no one ever changes the brake fluid.
i've seen cars go for 100k miles without them ever touching brake fluid.....and still the calipers get locked up from rust because of how brake fluid absorbs air..

 

I was just inquiring if the "Acura faithful" knew something about the Honda brake fluid that I possibly didn't in the application regarding Acura vehicles. That was all.

I mean, I do know the Honda power steering fluid is very specialized, as is the Honda coolant for this application. I know both work extremely well and offer outstanding long-life and usability for these apps. I just didn't know if the DOT3 Honda brake fluid wasn't somehow "specialized" as well.

 

i'm assuming it's for cost reasons? why use the honda stuff if generic dot 3 will do the same? I agree. that's why I use the generic stuff in my TL.

at one point in time, I was using Motul Dot 5.1 in my TL, but I did not see any benefit as I wasn't tracking the car.
the DOT 5.1 just had a higher boiling point than regular DOT3....meaning, one could do more emergency stops without brake fade.

 

Oh, and in regards to rust in the calipers, that is because of ripped or mis-installed piston boots more than anything else. I would even mention that redoing those boots in heavy-humidity conditions can contribute to them corroding.

Once corrosion works into the bore, then the seals will be compromised, which means moisture absorption through there as well.

If the boots are not installed with a sealant on the lips, there are a lot that don't have enough pressure throughout the sealing lip to make sure moisture can't get past.

Everything, always, comes down to the details.