Obviously it would take years for the % to get to 4%. (I dont think the line would be the weak spot given it is airless). rather the piston assemblies. the movement might allow water to contaminate past the seal, given the seal is designed to favor maintaining pressure on one side. ?. flushing and changing fluid every 5-10 years might not be a bad idea. if you are a purist. Id imagine a system could probably handle 10% water without much issue the tell would probably be a spongy pedal.
snoopy221,
Oct 3, 1:20pm
No Offence
But you really have ABSOLUTELY no idea. [And have NEVER changed brake fluid and checked it's water content]
mechnificent,
Oct 4, 4:38am
The fluid does absorb moisture out of the air. In the old days the reservoirs just had a metal or plastic cap with a hole in it, and then a rubber washer, also with a hole in it, to let air in as the fluid got lower when the shoes and pads wore. Now they have a rubber concertina without any hole in it under the cap, that can distort to allow the fluid to go down, without letting any air into the reservoir.
mechnificent,
Oct 4, 4:44am
Air, and so moisture, doesn't get in past the seals on the pistons in master or wheel cylinders when they slide because they are designed to prevent that. Despite Snoopy's contention that it does, it doesn't !
If they had a simple cup seal like a push-bike pump has then it would, but that would be stupid. air would get into your brakes every time you pushed the pedal down and then let it off again. Reason, and experience with those seals, quite apart from training, should make that obvious to anyone that works on cars.
Really makes me wonder some times.
jmma,
Oct 4, 4:54am
Come in sr2 :o)
theo35,
Oct 4, 5:41am
Sorry mechnificent but you are all wrong about this. snoopy221 and intrade are right on here.
Hygroscopic brake fluid attracts moisture. In a brake system. It can get to 2-4% within 1-2 years easy.
mechnificent,
Oct 4, 6:01am
I'm not wrong about why they have those seals. Snoopy's contention that a sealed reservoir wouldn't let the fluid into the master cylinder in the way a blocked, or undrilled return hole will, is ridiculous. given the rubber concertinas are concertinaed. And so is the suggestion that the seals on the pistons let air and moisture in. It doesn't happen.
I don't have a measuring dudah and have always judged the condition by eye, which is pretty much what the refractometry works on. I wouldn't know the percentages but I know fluid can go off on the shelf in the bottle, but I haven't seen it in the car in years.
And that aside, I haven't found water contamination or damage in probably twenty years, other than the odd four wheel drive that had been swimming regularly.
My car is a 1993 and I've had it eleven years, and yeah, slack mechanic, I don't change the fluid, which would have been years old when I got it by the general state of maintenance when I got it. I've never had any trouble and the fluid looks as good as new. And I know lots and lots of cars just like it. Change the fluid when you'r working on the brakes, doing pads etc I say.
mechnificent,
Oct 4, 6:15am
And finally. the proof, if any is needed of the efficiency of the sealed systems, is demonstrated by seeing how old vehicles, such as tractors, which don't have sealed caps, do still to this day get moisture into the fluid, and yup, rust the cylinders.
People really should be able to use their discretion. it's why we get trained. so we know and have that ability to make good decisions about what's needed and what will do another round. The work on a car should be done in a holistic way, taking account of it's age and design and use etc. Not just by some arbitrary schedule or policy being applied to all vehicles indiscriminately.
And I'm a very competent mechanic. I've been self employed almost continually since I was twenty-one and all my customers, and the three bosses I've ever had over my career have all decided within three months of my working for them that I was, to quote all three of them and the customers, "the best mechanic I've ever known/had".
The industry is full of parts fitters. It's a shame because they can't diagnose or even work carefully. Then they over charge to recoup their lost time, and it makes them rush even more to try and keep the charge reasonable. with more stuff ups resulting from the rushed diagnosis and repair.
snoopy221,
Oct 4, 6:18am
If ya gunna qoute Then the qoute you NEED Was provided by me in #40 As to your post 57 a simple READ of my#30 AND# 31 Your #54 well google and images of the bicycle pump and master and wheel cylnder seals. Ah BUT if ya OVERHAULED a FEW wheel and master cyls ya KNOW THAT. [Methink jmma does me KNOW sr2 does] ! .LOL Real World and HANDS-ON EXPERIENCE Tells ya When Ya In A Hole Stop Diggin! #40
phalanax,
Oct 4, 6:19am
Well I hope your sending it off to ESR otherwise your just wasting time. lol. Ive replaced/manufactured a few lines in my day. likewise the odd seal. let me see flush the lines. bleed from the furtherest point to the closest. does that sound like someone that wouldnt have a clue. lol Lets not overcook it. brakefluid aint exactly 10,000dollars alitre. lol
snoopy221,
Oct 4, 6:25am
re#58 AND#51
Anyone who has ever driven hard and KNOWS what excess water BOILING at brake temperatures FEELS LIKE.
mmmmmmmmmmmmmm Forget ya rust pal Tis akin to the disc pad that is 0.5mm and unable to take the load and heat and instantly the resin bonding it dissolves and steel is on steel Not cutey cutey for stopping Hence warrant requirements for minimum disc pad thickness
snoopy221,
Oct 4, 6:27am
oh and BRAKE temps can be a LOT hotter than the 100 Degrees ya water boils at Like a few thousand
mechnificent,
Oct 4, 6:30am
I'll leave it to the readers to use their own logic to figure out who's reasoning sounds correct Snoopy.
snoopy221,
Oct 4, 6:32am
Dry boiling point Wet boiling point Viscosity limit Primary constituent DOT 2 190 °C (374 °F) 140 °C (284 °F) ? castor oil/alcohol DOT 3 205 °C (401 °F) 140 °C (284 °F) 1500 mm2/s glycol ether DOT 4 230 °C (446 °F) 155 °C (311 °F) 1800 mm2/s glycol ether/borate ester LHM+ 249 °C (480 °F) 249 °C (480 °F) 1200 mm2/s [6] mineral oil DOT 5 260 °C (500 °F) 180 °C (356 °F) 900 mm2/s silicone DOT 5.1 260 °C (500 °F) 180 °C (356 °F)
snoopy221,
Oct 4, 6:32am
Wet boiling point defined as 3.7% water by volume.
phalanax,
Oct 4, 6:33am
It this an attempt to broaden the 'meth test' scam? I hope all those claiming scientific results are fully certified scientists. otherwise your results are just guesstimates based on off the shelf dodgy science.
snoopy221,
Oct 4, 6:39am
meth test LOL Reminds me of a new ! mechanic! at work one day. LOL standing there looking at a Tyre Machine With no idea . (ya know they just read about real world things-not see them and be expected to know how to USE them lol)
mechnificent,
Oct 4, 6:42am
Another Bob, that didn't listen to the lessons at the time.
And Phalanx. there is no need for guilt mate. Some people do bad things, to other people, quite deliberately and knowingly, that is a cause for guilt. But most things in life that we feel bad about, especially for good guys like you or I, that only warrants regret. not guilt.
phalanax,
Oct 4, 6:48am
Some of us dont need a tyre machine to change a tyre. lol. Was a time when folk used to reline brake pads/shoes. are there any of those places left?. probably the odd one here and there. Im not a qualified mechanic. but ive worked at a few old skool garages in my day. lol
intrade,
Oct 4, 6:54am
snoopy forget it . He changes the fluid and claims it never needs to be changed. .
mechnificent,
Oct 4, 6:55am
Trucks still reline their brakes. tractors. it is still done.
mechnificent,
Oct 4, 6:57am
If that's me you are referring to Intrade, you need to read more carefully. You are attributing words to me that I never said.
phalanax,
Oct 4, 7:06am
Lets not get into mineral oil braking systems. the '.Rolls Rroyce' of brake fluid lol
intrade,
Oct 4, 7:11am
why dont you just use water ? it only boiles at 100° shel be right mate.
mechnificent,
Oct 4, 7:11am
Citroen.
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