I have been reading a lot about racing brake fluid and its tendancy to absorb moisture faster then standard dot3. I would assume that our brake systems are fairly air-tight (correct me if I am wrong) So just where does all this moisture come from?

I would guess the resovior cap to be the weakest seal, so is this where the moisture is introduced?

What am I missing.

 

The air.

 

well, actually, I would say that the brake system kinda needs to NOT be air tight. While this may sound counter-intuitive, consider this:
as you use the brakes, the brake pads wear. That means that there is less material on the pad, and the pistons are "out" more. This will cause, as time goes by, the level of fluid in your reservoir to go down. If the system was air tight, that would be very difficult, as it would create a vacuum above the fluid level in the reservoir - and it doesn't. At least, I have never notcied a vacuum when I opened the cap!
So, to make a long story short (too late) the place where the air comes in is at the brake fluid reservoir cap, and as Willard pointed out, air is where the moisture is.

hopefully I am not totally full of crap.

 

I would hope the cap has some provision for this issue.

Will
-who will check his this evening

 

The only place you'll find "air tight" is outer space.

 

what if you pressure bled your system with pure Nitrogen
and minized water content in your brake fluid?


[Modified by Crazydave, 5:39 PM 4/16/2002]

 

Damn this is getting pretty ****. Just flush your brake fluid every year if your that worried about it.

 

LOL, I agree! That is all that is necessary.

 

its not that I am trying to be **** about it. I was just wondering. And since this is where you would find people the most "****" about their brakes that this would be the place to get an answer.

 

I use motul .. and I bleed it before every track day, and when I'm done

 

We are... thats why we bleed them mostly after track sessions and once or twice during the off season... or for me, every few autocrosses. Its not worth the hassle to do much else, since, well this works...

 

Ok fair enough.

If anybody wants Motul RBF600 my local moto shop sells if for 8.50 a bottle. I would be more then happy to pick some up for anyone who needs it. I'm guessing it would cost about 5 bux to ship two bottles via priority mail.

 

I think it comes thru the rubber too. While it seems odd, but rubber can contain moisture as well and transfer into the fluid. Its also not hard to believe when you see affects of condensation overnight.