Replacing brake fluid is one of the things your supposed to do. I don't know why I'm not reminded of this. Bought new car once, with maintenance manual. Wrote down all the stuff your supposed to do at intervals. Replacing fluid was something like 25k or some time interval. Why are they still using that old stuff.
Greg
No thanks. If your observations are correct then testing fluid at the master cylinder is mostly useless. But I don't know how much fluid actually circulates when brakes undergo normal use. Also says that brake lines should be flushed before long tern storage. I googled long term auto storage and by the third hit ran across recommendations that all fluids should be changed and topped, including brake fluid. Fits your observations.
According to the "hygroscopists" brake fluid gets loaded with water. Your views closely align with mine. It's corrosives other than water that does the internal damage - maybe copper, from what I've read. In any case, I still find no compelling reason to change brake fluid. Unless prepping for long term storage since you pointed that out. That's just my personal view. I've got nothing against it, and it's surely beneficial from a fluid chemistry/sediment standpoint. Just don't see the risk/labor/reward balance as being right. Which is in line with what the manufacturers said in the link I posted.
Clean brake fluid, both hygroscopic and hydrophilic, in the absence of water is not a concern in the environment of a sealed system as without the latter, the former does not promote the formation of corrosives that attack metal surfaces, a clear example being new product, although now mainly found in polyethylene bottles, formerly underwent long term storage without incident in metal containers.
The main constituent of the sediment commonly found in the system is hydrophobic zinc stearate, a byproduct of the interaction of zinc oxide and the otherwise largely benign stearic acid that permeates from the rubber seals.
I've yet to see any cogent analysis of brake system chemistry. Probably too many different metals used by various manufacturers to make it worthwhile. Different seals. Different heat with different systems too. I'd guess manufacturers give suppliers some acceptable range in the alloys, so there's more differences. I have seen mention of copper leached from brake lines reacting with other brake systems metals causing corrosion. Don't think water had to be an agent in that corrosion, but can't swear to that. Also seen mention of chemical reaction with seals being a cause of corrosion. There's all kinds of stuff about it on the net, most of it looking like haphazard speculation to me. Anyway, the reason the "hygroscopists" usually give for doing brake fluid changes has nothing to do with corrosion. It's nearly always "your water contaminated fluid will boil leading to brake fade." That's clearly ridiculous to me, and always has been. I can buy the "change to prevent corrosion" argument. Not enough to do brake fluid changes, but it's a valid argument. Won't keep wheel cylinders/caliper pistons from rusting due to water intrusion past the outer seals either. And it doesn't change the fact that all my brake line failures have been due to external rust. Since I'm "almost" a fluid change freak - only because I do sometimes think about it - I'm a little jealous of those who change their brake fluid. But not jealous enough.
Brake Fluid Sediment Caused by Rubber Cups
Standard No. 116; Motor vehicle brake fluids
Don't think I'll buy that book.
Nothing new there. In that link I posted Ford tested brake fluid in their vehicles (unspecified) and found water was 1-1.5% after 7-10 years.
Thanks. Pretty detailed test procedure. 85,000 strokes. In a "simulated" brake system. Useful for DOT to set the standard for new brake fluid performance, but doesn't tell you anything about what's happening in your car's internals. I really hope DOT is leaving most of that testing of new brake fluid to the QC departments of the producers. The gov inspector that watched me package nitrogen infused soup mix powder for the military was mostly dead weight. I can't recall him ever catching anything amiss. Maybe because his presence kept me on my toes. I'll never know. And I won't know what's happening inside my brake systems until something gives up.
Yes it has always been my suspicion that the rubber
reacting/dissolving in brake fluid was the source of
corrosive sediment. But is there evidence this has
anything to do with water?
If any of my cars had a dual-diagonal setup I probably would not bother either. But they don't so I do.
Water can and does oxidize brake fluid. In addition, water, when added to many acids, (up to a point) commonly potentiates (as elevated temperatures also increase the rate of ) its corrosive effects. Moisture in the system is detrimental for multiple reasons. But it isn't my goal, nor do I have an interest in attempting, to convince those unwilling to accept these facts and I accordingly won't continue to needlessly repeat and provide support for them after this:
"Brake fluids are composed of many combinations of base lubricants, solvents and inhibitors. In current fluids base lubricants are generally polyglycols or castor oil derivatives; solvents are glycols, glycolethers, or alcohols; inhibitor combinations include alkaline materials and antioxidants. Upon storage, the corrosion inhibitors may interact, deteriorate, o.- become depleted by contact with metals in the containers, by presence of water and oxidation products in the fluid, or by fluctuating temperatures. If the inhibitors are consumed, corrosion may then take place."
That looks more like innuendo - not evidence. It says things may happen. That implies they aren't sure if they do. In the case of undisturbed sediment, corrosion inhibitors may get used up locally in the sediment and as long as fluid
isn't stirred up corrosion can take place.
The facts seem to be that sediment settles and corrodes wherever or whenever there is no movement of the fluid in parts of the system. Obviously the age of the fluid and probably the age of the rubber components is a factor, but I haven't seen any evidence that water plays any significant
factor. A sealed system that sits for a couple years isn't much different than fluid sealed in a can, except that the
fluid that has been in use for a while has dissolved rubber that will settle out and gravitate to the lowest point when it sits for a long time.
That looks more like innuendo - not evidence. It says things may happen. That implies they aren't sure if they do. In the case of undisturbed sediment, corrosion inhibitors may get used up locally in the sediment and as long as fluid isn't stirred up corrosion can take place.
The facts seem to be that sediment settles and corrodes wherever or whenever there is no movement of the fluid in parts of the system. Obviously the age of the fluid and probably the age of the rubber components is a factor, but I haven't seen any evidence that water plays any significant factor. A sealed system that sits for a couple years isn't much different than fluid sealed in a can, except that the fluid that has been in use for a while has dissolved rubber that will settle out and gravitate to the lowest point when it sits for a long time.
********************************I'll violate my above promise, but just this one time, as I don't care to be corrected by such a clearly incompetent assessment. But sans any documented evidenced to the contrary, I won't again respond nor further comment. You'll kindly forgive me for explicitly stating that which is so glaringly conspicuous, but you quite obviously don't begin to understand even the most basic fundamentals of chemistry, and would appear to have substantial difficulty not only synthesizing knowledge from those spoonfed to you but also in comprehending what you read.
"Effect of Water on Oxidation Stability of Brake Fluids - Twelve brake fluids meeting Federal Specification VV-B-
680 were subjected to the oxidation stability test outlined in paragraph 4.5.14 of Federal Specification VV-B-680 except that it, one test 0.5% Benzoyl Peroxide tvas added to the broke fluid and in the second test 0.5% Benzoyl Peroxide and 5% water was added. In the specification test, only 0.2% Benzoyl is added. Th,; excess peroxide decreased the stability to borderline values so that the effect of water would be more evident and more pronounced. The test specimen! were visually examined for evidence of corrosion (pitting. etching, discoloration) after ten days stnrage at 158*F.""Effect of Water on Oxidation Stability of Brake Fluids - Water greatly reduces the oxidation stability of brake fluids, as shown in Table V. In the tests recorded in Table V, the level of Benzoyl Peroxide was raised to the point where one of twelve brake fluids exhibited excessive corrosion of test specimens. Several of the other fluids were borderline. With added water, three fluidsshowed excessive corrosion of test specimens and nine of the twelve fluids showed inrreased corrosion over the cests without water."
"The problem of brake fluid stability is also becoming increasingly evident. During the past few years large numbers of reports have been filed concerning gumming and corrosion of brake parts in military vehicles. This report shows that the chemical breakdown of the brake fluid Is accelerated by the presence of water and studies toward the solution of this specific area of difficulty should continue."
Moisture may well be detrimental. But as Vic pointed out
earlier Ford did tests and found that moisture content in the fluid of 7-10 year old cars was negligible.
All you have demonstrated is that if you intentionally add water to your fluid you will have corrosion problems.
So don't add water.
I still haven't seen any evidence that water has anything to do with the corrosion to brake lines when a car is left to
sit a long time.
-jim
Back in the late 1970s I bought a 1954 Ford truck. One morning when I started that truck up and I mashed the brake pedal, the pedal went all the way to the floor. The right rear side brake line had rusted out. Don't take chances with your brakes.
indeed. i knew a manufacturer who made copper/nickel tube that was very strong and highly corrosion resistant - ideal for brake lines. they tried to sell it to the auto industry, but they weren't interested. it wasn't price, it was simply the fact that it would last too long. and the industry said so!
not a valid test on many cars - they have load compensators as part of the brake proportioning system. if the compensator works, it'll cut line pressure to zero if the wheels are off the ground.
not all stainless is good against salt corrosion - ask a sailor. it needs to be the right grade. and frankly, there are better materials for this application. heck, even ordinary steel lines are ok if they're plated properly - but that's hardly ever these days.
it's pointless trying to use rustoleum /and/ converter - rustoleum contains its own converter already.
cheap cost-cutting manufacturers have no problem saying there's no point changing the brake fluid on a car because they don't want to car to last too long anyway. particularly when it causes expensive maintenance that is a source of part sales income when it's out of warranty.
but in the real world, water still diffuses into the hygroscopic brake fluid regardless of the materials they say their lines and seals are made from. this moisture saturates the brake fluid, and if left unchanged, causes corrosion and reduces the working lifetime of parts. regular fluid replacement, typically on a two year schedule, will keep the moisture content of the fluid down to a level that the fluid can neutralize. and which won't cause boiling on heavy use. if you extend beyond the two year absorption time, all bets are off. and in the context of the safety issue, that's insane.
moisture's effect on brake fluid boiling point and therefore risk, is not a matter for debate or opinion, it's a matter of fact.
if that test and result data are not "evidence", then it's hard to see what else might qualify.
no, it observes the facts of what /does/ happen - there's no ambiguity whatsoever.
it doesn't look like you read the same paper as everyone else, because there's no uncertainty in the paper cited.
the paper doesn't address sediment corrosion in use, just long term stability of fluid in storage. again, it doesn't seem that you're reading the same paper as everyone else.
then you're not looking.
not true. most brake fluid systems are open to atmosphere above the reservoir, and the hoses and seals in a system offer significantly more surface for diffusion than the small amount of polymer in the lid of a can.
seal rubber is a cross-linked polymer - it doesn't "dissolve". it wears and that wear product can be held in suspension [like the fat in milk] or it can sediment out [like tea leaves].
don't try to confuse him with facts, his mind is already made up.
no, frod did tests that determined that no serious failures occurred within the average first owner's possession of the vehicle and thus they could dispense with the service recommendations that might cost them money.
second owners don't get the same warranty rights of course, so they don't count and frod are happy to sell them replacement braking systems all day long.
no, water diffuses in through seals, hoses and the top cap. it's impossible to stop. and it's definitely not deliberate.
you can't "see" anything if your eyes [and mind] are shut to all the facts that contradict what are simply your underinformed dogmas.
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