Brake fluid change.
Back in the seventies I used to work on the marketing of brake fluid.
It is true that the fluid is hydroscopic (or was that hygroscopic?) and slowly absorbs moisture from the atmosphere.
In extremis - descending a series of steep mountain passes at very high speed on a hot day - this just might start to boil at the calipers and reduce braking affect.
At the time the engineering opinion was that such an occurrence was so unlikely to occur as to be, to all intents and purposes, disregardable.
However it was a damn good ploy to sell more fluid and for the garages to sell more labour. And as there was always existed that outside chance, then nobody could accuse us of scaremongering for profit.
Needless to say I have never had my brake fluid changed, other than the one occasion where a garage I had good relations with, changed it off their own bat. I hadn't the heart to make them take it back out.
I'm still alive.
Rob
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>>At the time the engineering opinion was that such an occurrence was so unlikely to occur as to be
It happened to me in a Dodge Ram. Very worrying, although it was in the Andes and so somewhat more extreme than the UK. However, I change the brake fluid, it doesn't cost that much that I'd risk it.
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Got the car back late this afternoon - total cost (including brake fluid) £198 - gulp ! The price you pay for a 3 year warranty !
Work included -
Oil (semi synth) & Filter
Fuel Filter
Pollen Filter
Air Filter
Brake Fluid
Key Fob Batteries
Car Washed !
Service book was stamped, and AA recovery paperwork done ! All very efficient, unlike the last time the servicing was done at this dealer.
Once got the car home checked that all this had actually been done (call me a cynic) - to see lovely shiny new white filters in place - amazing !
Happy(ish - appart from £200 down !)
Steve
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Rob - it's not just the possibility of boiling at the caliper; don't forget the internal corrosion as the fluid gets wetter.
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So how does brake fade occur then? Is that something different?
It happened to me in my old Fiesta (terrible brakes) when I was er... following my dad in his Micra, forgetting that his P reg car was just a shade better engineered than mine. Quite frightening to feel that spongey totally useless feeling through the pedal.
Blue
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No, that's brake fade and it's happened to me. I've also managed to go through a set of discs in 9k in a Fiesta (98) and 15k in my R19.
Incidentally, I drove my 14 year old Renault 19 at 50 in a 50 limit and left it to the last possible moment to brake to the 30 limit I was going into. (Irresponsible I know but there was no traffic). Where my nerves gave out I hit the brakes and was doing 27 at the sign.
I then repeated the experiment in the Focus and, from basically the same place, expecting the brakes to be much better, ended up doing 29. There's a lot more pedal travel in my car, which is normal in cars of its age compared to modern cars, but it appears that there's nothing wrong with the anchors themselves.
Mark, if you saw a grey R19 doing emergency stops in RLBS this weekend, it was me. (Actually only did one, when the traffic lights changed on me at the last second and I decided not to risk going through on amber. This is why I use so many brake discs.)
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Sorry guys,
No use asking me technical questions about rusty calipers and the like. I'm just a marketeer.
All I can repeat is that the technical bods, the guys actually in charge of product development at one of the countries two largest brake manufacturers just laughed (nearly politely) at the thought there could be any real probability (East of the Andes) that the sort of volume of water absorbed by brake fluid over the lifetime of a car could pose any real threat to the vehicles safety.
It was a theoretical, minute possibility only, but sufficient for a marketing campaign to boost overall sales of fluid.
Rob P
Don't you need oxygen as well as water to promote rusting?
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Rob - yes you do need oxygen, but if you can't keep out the water you certainly won't keep the air out!
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9K out of the discs on a 98 Fiesta! :O
I've just had mine serviced at 9K and it was absoloutely fine, apparently all was well, even the tyres despite the fact that they are going bald on the outside edge, apparently it's the central section that counts or something?
Seeing as they could've easily had a sale simply by telling me it needed new ones I can only assume that they're right...
Blue
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Blue,
Tread requirements are 1.6mm over the central 3/4 of the tyre and visible tread on the remainder - all the way around the circumference of the tyre.
If you're scrubbing the outside edges off the front tyres then the car is probably running too much toe in (unless you live in Milton Keynes are particularly 'enthusiastic' at the myraid of roundabouts!). Might be worth a trip to one of the tyre places and getting them to check the tracking on the front.
As to your earlier question about brake fade this is caused by heat build up in the pads and discs which causes the braking efficiency to fall off markedly - it tens to make the pedal feel spongey, and the brakes appear to stop working as well. They probably start smelling a lot as well, and may smoke if you really push it (been there done that!). If you boil the fluid the pedal hits the floor and you have to pump it 3 or 4 times ot get any braking effort. (Been there done that as well - it's somewhat frightening!).
Richard
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Cool! I don;t think I boiled the fluid, if I had my rear brake lines would probably have given way and then I would have found out how well the split circuit emergency braking works (or not)!
Blue
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Haha
That reminds me of a vectra i once hired. The brakes were absolutely smoking when i had finished and I drove in to return it. i stopped and it absolutely stunk so i drove off again to let it cool down/stop smelling and then took it back.
Has anyone ever had brake failure because of old brake fluid as opposed to not enough? I doubt it. Certainly never heard of it, and I've run cars that I know the brake fluid is at least seven or eight years old (probably more).
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So we don't need to change brake fluid, just top it up? Is that something I can wipe off my (as yet unwritten) service list?
HF
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HF - I would worry if your brake fluid needs topping up.
My dad's car is 7 years old and the brake fluid is at the same level as when we bought it new.
Worth checking now and again though, I suppose brakes are a fairly important part of the car. :)
I found out mine are still well capable of locking the wheels when a cute little dog decided to try suicide. I'm pleased to say that I pulled up to a skidding halt with room to spare before knocking it into next week. :)
Is it normal that only one wheel locks during braking? Not that I stop sharply very often, but when I do, it always seems to be the right hand wheel, even when the car was new...
Blue
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I recently had my car (not a Vectra) serviced and got them to change the brake fluid (car is 6 years old) - what a difference in stopping power. Seriously, for the added safety and given it's probably about £15-20 just get it done I would say.
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Some one mentioned internal corrosion,to continue if the car has ABS changing the brake fluid every 2 years is a lot cheaper than a ABS unit at £500.
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There seems to be a lot of guessing going on here :)
"Some one mentioned internal corrosion,to continue if the car has ABS changing the brake fluid every 2 years is a lot cheaper than a ABS unit at £500"
How easy you lot all make the marketeer's job.
Thanks
Rob
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Every time I have replaced brake fliud the difference in the feel of the brakes was significant and for the better.
I recon it must also help lubricate the seals and prevent corrosion. I remember replacing leaking rear cylinders on a 1980 golf due to loads of rust. The fluid was really cloudy and contaminated.
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Oh OK.
I know I said I wasn't technical, but even I know that water is as uncompressible as hydraulic fluid.
If there is water in your fluid you won't know it is there until halfway down the Andes.
If your brakes feel better after a fluid replacement it means that AIR has been removed from the system.
This can be achieved with a small length of rubber tube, a nipple spanner and a jam jar. Total one-off cost of about two quid if you doun't count the jam (Or even if you do and it is Tesco Value)
But you guys seem so desperate to spend money on brake fluid and labour, who am I to stand in your way?
Rob
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>>If your brakes feel better after a fluid replacement it means that AIR has been removed from the system.
True, but that air is probably wihtin the brake fluid as rather a lot of minute air bubbles, which will typically only come out with a change of fluid. Bleeding won't get them, unless you do it for so long the brake fluid is changed of course.
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Rob - you don't have to spend money on labour - do it yourself with the same jam jar etc. Just needs a new can of fluid.
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A good point. You only have to look at the colour of, and residue in, old brake fluid to understand how it deteriorates. The residue has to come from somewhere - worn seals usually. So you replace the seals & bleed the whole system - ergo, complete fluid change! And no, I have no marketing connections, just a few years experience.
I can't understand why so many people are quibbling about the small cost of a brake fluid change - if it costs £15 every couple of years to potentially save your life, or indeed an innocent third party's, surely it's worth it if there is any element of doubt.
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"surely it's worth it if there is any element of doubt."
Absolutely.
Your the guy with the doubt, it is worth it to you.
I'm just offering you the facts.
Rob
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"True, but that air is probably wihtin the brake fluid as rather a lot of minute air bubbles"
Ah,
This would be some special kind of air that holds itself in suspension in a relatively dense fluid then, unlike the normal kind of air that floats to the top?
Are you sure you're not getting confused with scuba diving and nitrogen narcosis / bends?
Rob
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The brake fluid change during the service has made a significant improvement to the feel of the brakes - the pedal is now much firmer, and now feel I can modulate the braking effect with more accuracy. As for the cost - 15 quid out of 200 - who cares ? I would much rather get the job done "professionally", with a guarantee, than taking off each wheel and fiddling with the braking system - something I am definitely not qualified to do !
Steve
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Rob - there's no need to sow doubt in the minds of those who intend to carry out preventive maintenance on their cars. If you choose not to, because many people get away without, and it saves you a few quid, that's your choice.
And maybe the bubbles do rise to the top, but that 'top' is the rear brake cylinder for example, where they can't escape. That is the sponginess in the pedal.
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Not just the Andes;
Holiday 2 yrs ago, campsite at foot of Alpe d'Huez road (of Tour de France fame. Air temp 30 celcius, strong sunshine, fellow camper's Vaux Astra suffered brake failure in descent, most likely from this cause.
Perhaps in the past fade got them first, but if my cars were not both Citroens with mineral oil hydraulic fluid I'd be religious about this.
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>This would be some special kind of air that holds itself in suspension in a relatively dense fluid then, unlike the normal kind of air that floats to the top?
That would be about the gist of it. Unless of course you have some special kind of brake lines which are totally vertical allowing it to float to the top ? Sadly mine wander all over the place and changing the brake fluid is about the only way to get it all out, especially since when not in use it floats up into loads of different air bubbles in different high spots, but as soon as you use the brake pedal, even for bleeding, it all gets mixed back up again.
Or do you have that special brake fluid which causes the air bubbles to flow sideways ?
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Ah thanks Mark, that's much clearer now.
So your braking system is in such a condition that large (?)quantities of air keep getting into it.
When you bleed the system at the calipers the air, unlike any I have seen, doesn't progress in discrete bubbles along the tube into the jam jar, but mixes itself into the fluid?
Finally the pedal reaches the required firmness, you tighten the bleed screw and this finely mixed air which has been pretending to be non-compressible (In order to give you the firm pedal response) suddenly goes back the being its normal, compressible self. Or is it that once a bubble of air reaches a required smallness it becomes non-compressible? Or is it that once it gets into these 'high-spots' it suddenly starts to change its physical properties? Sorry I am trying to keep up, but I'm struggling.
I said I wasn't technical, your help is invaluable.
Anyone else got any theories?
Does anybody think we should we change our power steering fluid every 20,000 miles just in case?
Rob
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Why are you so worried about it ? It makes me feel safer that its changed. I very much doubt if you *know* whether it should be or not. So for a tenner or so every couple of years, I'll carry on changing and *know* there isn't a problem, or at least not that one, and try not to worry about my financial loss of less than 2p per day.
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Like I say Mark, it doesn't 'worry' me at all.
I am just so fascinated to see a marketing strategy that I was part of back in 1974 or '5 becoming so shrouded in myth and legend that it is now taken as some sort of gospel. So just a personal interest really.
My university thesis was on 'diffusion of innovation' and to be so closely involved in the development of something from a market expansion strategy to a 'safety' principle you have to admit is intriguing.
And the myth will now accelerate thanks to the internet. How many people will in future hear "Ah there was a discussion on this on the HJ site. Apparently you can wreck your 500 quid ABS if you don't change your fluid every service" It could be the birth of an urban legend. Such is the effect of half-remembered snippets.
I'm sure everybody is heartily bored of this now so I will sign off with one other small piece of 'horses mouth' information.
(Restatement) The problem with brake fluid is the fact that is is aggressively hygroscopic, so pulls moisture out of the atmosphere that is then absorbed into the fluid. Under extreme circumstances this can boil at the caliper causing a reduction in braking effect.
The greatest advance since my time working in the industry has been the introduction of translucent plastic master cylinder resevoirs, so that the level can be monitored WITHOUT OPENING THE CAP and exposing the fluid in there to the air. Yes it really is that aggressive.
Now the fluid in your nice new motor has been filled at the factory from bulk containers under conditions that prevent more than minimal absorption.
What do you reckon they use in the High Street Dealership?
Usually 5 litre cans.
So, unless you happen to be lucky enough to be the first motorist whose fluid is changed from that can, your 'safety critical' fluid change will be replacing the factory fluid with 'fresh' fluid that actually has a higher moisture content, not lower.
Under these situations you are making the 'safety' situation worse, not better. So much for good intentions.
Finally, if you need to top up your reservoir and you really are concerened about all these innocent third parties you might be about to maim and kill.
1) Use a fresh tin
2) Do it quickly
3) Throw that tin away. The remaining contents will have absorbed plenty of moisture already. There is no point in keeping it on the shelf.
Bye for now.
Rob
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Ok, you three points make sense. But, and you knew there'd be a but...
I have changed the fluid and its dirty and kind of cloudy. Now admittedly if it sits in the bleeding jar on the shelf the air rises out of it and the rest of the stuff settles. But that takes time with it being undisturbed. A brake system is active and doesn't get left undisturbed in order for any air to settle out.
And the fluid must drop, and air must at least enter the resevoir as the brake pads wear. And I wouldn't say its going to wreck anything, only that the braking ability at the wheels changes differently from one wheel to another, and therefore the car is going to start not braking straight.
It might be minor, there might only be a slight chance. But just to be safe I'd rather so it anyway, and even if all it does it makes me feel better, then it was money well spent.
And you're probably right about the interest level in this thread, so I shall leave it there as well.
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One wonders if there is a way of adding a "dessicant" of some description to the brake circuit - any chemists out there know of a substance which can remove water from brake fluid?
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