brake fluid really need to be changed?

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"The reason the brakes got soft was not 'pad fade' though the car did have some of that, too. The old fluid had a high level of water which caused localized boiling at the calipers. This requires more volume of fluid flow from the master cylinder and eventually I ran out of brake pedal travel. "

still makes no sense. The master cylinder has a LOT more volume that the wheel pistons.
 
Yes ..but you've only got one stroke on the pedal. It's not like a leaking wheel cylinder where you can "pump 'em up" by just pushing more fluid down the line. The air bubble that water creates expands as you relieve pressure on the pedal.


but I still think this is sorta worrying about really short nasle hairs offending your date (as though she's gonna really look that far up there).
 
My words are probably falling on deaf ears for the most part. If the hardest you guys ever push your braking system is a 500 foot 65-0 on an exit ramp, then I can see why your brakes "work just fine." I push all the systems in my car to the limit and I want them at peak efficiency or else it's just sheer abuse.
 
quote:

Originally posted by kevm14:
My words are probably falling on deaf ears for the most part. If the hardest you guys ever push your braking system is a 500 foot 65-0 on an exit ramp, then I can see why your brakes "work just fine." I push all the systems in my car to the limit and I want them at peak efficiency or else it's just sheer abuse.

No I don't abuse the public highways by driving like a maniac.
 
kevm14

No one said that there was anything wrong with being anal about brake fluid ...the only debate is with "required" elements of the stuff ...a term victim of subjective review.


Take a look at "Monk" ...is he wrong for being the way he is???
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(yes, I'm just kidding
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From FMVSS 116:

Dry BP
DOT3 205C
DOT4 230C

From the curves in my BOSCH Automotive Handbook:

Water % -> 1% 2% 3% 4%
DOT3 175 150 130 120 C
DOT4 230 190 170 150 C

Small amounts of water can really drop the BP of the fluids, especially DOT3.

The fluid will not boil under the high pressure present when applying the brakes. But, when the pedal is released, the system is vented through the small vent hole in the MC, resulting in atmospheric pressure in the system. That's when the fluid in the calipers can boil, and push some fluid out. The next time you apply the brakes, you just collapse the bubble without much pressure buildup or braking.

Personally, I don't take chances with brakes, when it comes to maintenance. I replace the fluid every year, via a good flush...about 1 qt per corner...DOT4 only.

I always buy new fluid when I use it, and never store it with or without the seal broken.
 
If you want to waste your time and money changing brake fluid and maybe creating more problems than you solve, go ahead. Just do the necessary brake maintenance too, and quit insisting changing fluid substitutes for maintenance.
 
quote:

quit insisting changing fluid substitutes for maintenance.

labman, I am afraid this is going to fall on deaf ears, but let me say this in the nicest possible way: I'd really like to put this part of the discussion for once and all behind us. I don't think anybody in his right mind has insisted on neglecting brake maintenance beyond a brake fluid change. If you truly believe this type of neglect is what's going on, then I urge you to reread the many threads we've had regarding brake fluid changes. As far as I am aware, nobody ever said a brake fluid change was going to magically prevent or even repair worn or defective parts. I implore you to not confuse seperate issues. I am sure we can respectfully disagree on many issues, including the merits and risks of regular brake fluid changes. But please lets not confuse the issues at hand.

I think it might be a good idea if you, or anyone, were to start a thread about brake maintenance procedures, tools needed, and apocryphal stories, because I am sure your expertise in this area is very valuable and of interest to all of us. I just think we need to seperate the "fluid service" from the other and at least equally important brake maintenance issues, because it will allow us to discuss the matter without getting into each others hair all the time. I hope my suggestion makes sense and that I didn't just waste five minutes of my time.
 
I am taking an advanced Suspension, Brakes, and Steering class at my local college. My instructor of 35 years in the brakes area says that drum wheel cylinders should be either rebuilt or replaced with every relining or shoe replacement. At the very least, the dust boot should be lifted and checked for fluid leaks. The rubber cups on the inside wheel cylinders tend to leak [more so than disc calipers do]. Dust boot seals can become contaminated with leaking fluid and would need repalcement anyhow. Just as with calipers, it may be cheaper to buy new wheel cylinders instead of rebuilding the old ones.

On disc calipers, the caliper should be checked for leaks periodically and with every pad change. If the dust boot is torn or cracked etc, it should be replaced. Replace if it leaks of course. With the amount of labor it takes, plus boot/seal kits [and possibly a new piston; ford uses phenolic plastic on some models] and honing, it is usually cheaper to buy a new rebuilt [either loaded or unloaded] then to rebuild the current one.

He reccomends that fluid be replaced every 2 years or 24 months; brake fluid becomes corrosive partly because of moisture content, but more over because of depletion of the corrosion inhibitors. I found this a good read

Brake lines will have to be replaced on an interval that dpends on your climate; if you live somewhere where they salt the roads a lot, then you can count on rusted lines.
 
quote:

ChrisW:
..... My instructor of 35 years in the brakes area says that drum wheel cylinders should be either rebuilt or replaced with every relining or shoe replacement. ....

Did he tell you why?

With drum brakes the pistons move outward as the linings wear. Moisture, which drops to the low points in the hydraulic system, behind the pistons pits and corrodes the cylinder. When you put new linings in, the pistons are now working where the pits and corrosion are.

If they were not leaking before the relining, they will be soon after.

So you pull the cylinders apart and run a hone through them to remove the gunk and smooth the bore. If, after that, there are still pits or the pistons are too loose in the bores, you replace the cylinders.

Flushing the system every year or two helps head off the pitting and corrosion.
 
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