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I also consider two years too soon and five is a good compromise unless arduous driving conditions such as towing perhaps. You will get a range of views from do it now to leave it until the car is sold.
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On modern manual vehicles it is more a hydraulic fluid than just brake fluid as it is shared with clutch system,
Like all preventative maintenance you decide what is acceptable, It can appear an unecessary expense every two years if you do low mileage.
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DOT4 dry boiling point is 230C. The wet boiling point (3.7% water...why 3.7?...no idea) is 155C. Modern brake systems are well sealed, including the reservoir which has a specially designed cap so moisture doesn't get in. I have never changed my brake fluid as I do not believe it has absorbed anything like 37mls of water per litre. And even if it has, I cannot envisage a situation where it will even get as hot as 100C, unless I plan to descend an alp with the TR7 towing a heavy caravan.
Apart from the conflict of interest of mechanics wanting to do as much work as possible, I suppose such cautious recommendations stem from the time it could boil more easily in the old days of brake cylinders which lived inside hot iron brake drums, now rarely seen on the front wheels which do most of the braking. But with discs the fluid in the caliper is well away from the heat source. Also, the hollow structure of its piston is designed to minimise heat conduction from the pad back plate. I've never had a problem with caliper corrosion either, as modern seals are so good and I ensure pads and discs are fully worn before changing them so that the piston eventually travels most of the full length of its cylinder.
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Thanks for the advice. This is pretty much where I am on this. It has only done 15000 miles of mostly motorway driving anyway and the braking is absolutely fine. I am only intending to keep it for another year to 18 months so will leave it.
Edited by davecooper on 21/08/2023 at 17:59
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"It has only done 15000 miles of mostly motorway driving anyway and the braking is absolutely fine."
Cant think of any reason why brake fluid deterioration would be affected significantly by mileage. It'll depend almost solely on elapsed time.
If you filled your braking system with tap water, the braking would similarly be absolutely fine, until it wasn't.
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I agree 2 years is a bit keen, but the useful thing about doing this job say at 3 years is the bleed screws don't get the chance to corrode completely in place, many of us will recall the gloom of finding a bleed screw snapping off and traipsing off to find another caliper or slave cylinder and then the joy of how far down the brake circuit we'd have to go to find a pipe that actually disconnected without chewing the brake line up...arrgh.
What i suggest is far more important is every other year at least a full strip clean and lube up of the brakes, a rare thing to happen at a main dealer unless you are paying extra, personally unless you DIY such work i'd pay a trusted indy to do the full brake service and renew the fluid at the same time. if his charges are more reasonable.
edit, only keeping the car for another short while? yes leave it.
Edited by gordonbennet on 21/08/2023 at 18:06
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I put PTFE tape on the bleeder threads. Have to be careful so bits of it dont get into the system and start acting as non-return valves, but thats avoidable
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John, do me a favour, go for a spirited drive in your Audi, stop and immediately touch the calipers....bet you can't keep your hand on them.
Have you ever noticed after a drive in the rain that your front wheels are dry along with a good portion of the tyres? Wonder why that is? Can't be centrifugal force can it as they've been rotating at the same speed as the wet rear wheels and tyres.
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John, do me a favour, go for a spirited drive in your Audi, stop and immediately touch the calipers....bet you can't keep your hand on them.
Took the Audi out today for several small country road miles, tried to use the brakes more than usual on return. Couldn't reach the inner working side of the twin pot caliper behind the wheel but the outer bit was cold and I could even keep a wet finger on the ventilated disc (I expected it to sizzle but it didn't).
Have you ever noticed after a drive in the rain that your front wheels are dry along with a good portion of the tyres?
Nope.
Have you ever noticed how large modern pads are? Partly for longevity and partly to not get so hot as the early tiny pads did (like the ones on my TR7 with small unventilated discs).
Have you also noticed that most cars now have large ventilated front discs? These are slow to heat, dissipate heat quickly and thus minimise the chance of retained heat being conducted through the pad, pad back plate, hollow front part of the caliper piston and eventually to the brake fluid. All part of modern design to keep brake fluid and heat apart from each other.
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Have you also noticed that most cars now have large ventilated front discs? These are slow to heat, dissipate heat quickly and thus minimise the chance of retained heat being conducted through the pad, pad back plate, hollow front part of the caliper piston and eventually to the brake fluid. All part of modern design to keep brake fluid and heat apart from each other.
And these ventilated disks suffer from internal corrosion, as I think you noted recently. All part of modern design that caters to the "masterly inactivity" of the punter, ideally building in a bit of obsolescence at the same time.
However, maybe even modern designers didnt specifically do this so you never need to change your brake fluid. Its more likely to reflect the higher performance of modern cars.
If I'd ever had ventilated disks, I would probably have attempted to rust treat them internally with sunflower oil and aluminium abrasion, but one would have to careful of potentially contaminating the pads with spun-out oil before it polymerised, and if the disks got very hot it'd burn off anyway.
On the whole I think I preferred solid disks and changing my brake fluid every few years.
Just seemed more solid, somehow.
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........all part of modern design to keep brake fluid and heat apart from each other.
And these ventilated disks suffer from internal corrosion, as I think you noted recently.
I did - after vigorously probing each ventilation channel with an old screwdriver.
If I'd ever had ventilated disks, I would probably have attempted to rust treat them internally with sunflower oil and aluminium abrasion.....
As you surmise, probably ineffective. But how on earth would you abrade them internally?! Anyway, they should be good for another eight years/16,000miles.
On the whole I think I preferred solid disks and changing my brake fluid every few years.
While I was at it, I (easily) undid the bleed nipple slightly on one side and forced a few mls into a clear glass spice jar. Colour and translucency as new, unlike the sludge in your photos! So I didn't bother with the other side.
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........all part of modern design to keep brake fluid and heat apart from each other.
And these ventilated disks suffer from internal corrosion, as I think you noted recently.
I did - after vigorously probing each ventilation channel with an old screwdriver.
If I'd ever had ventilated disks, I would probably have attempted to rust treat them internally with sunflower oil and aluminium abrasion.....
As you surmise, probably ineffective. But how on earth would you abrade them internally?! Anyway, they should be good for another eight years/16,000miles.
On the whole I think I preferred solid disks and changing my brake fluid every few years.
While I was at it, I (easily) undid the bleed nipple slightly on one side and forced a few mls into a clear glass spice jar. Colour and translucency as new, unlike the sludge in your photos! So I didn't bother with the other side.
Speculative, since I don't think I've ever had ventilated brake disks, and probably never will, but I would probably try some wire in a power drill chuck, which should rattle around inside quite nicely, I made up a length of stainless steel stuff with hooks on the end when I was coal mining in a borrowed Honda Accord EGR system that might do, with the finger loop snipped off or crimped flat
Then I might follow up with some aluminium wire and vegetable oil.This is sometimes used (without the vegetable oil) for welding cables and some railway signalling functions because its less attractive to thieves than copper, unless the thief is me. They built a new railway bridge near here after typhoon damage to the old one, which still had some of the cabling in place, a year or two ago. plus some authentic USAAF bombing and strafing damage.
Or I THINK they sell thickish wire for bonsai that might be aluminium
Heavy gloves and eye protection de riguer in case the wire gets away.
Re your shiny clear brake fluid, MIGHT be fine, but I'm not convinced, mostly because my brake fluid was similarly shiny while the system was full of corrosion sludge, which, as I said, was not removed by high pressure bi-directional flushing (using an enema syringe and pushing as hard as I could on the piston, causing a noticable up-welling in the master cylinder) for several system changes.
Didnt shift it. Needed stripped and cleaned
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......... I would probably try some wire in a power drill chuck, which should rattle around inside quite nicely, I made up a length of stainless steel stuff with hooks on the end when I was coal mining in a borrowed Honda Accord EGR system that might do, with the finger loop snipped off or crimped flat
Wouldn't work as the channel ends in a slight dog-leg with the narrow exit hole pointing inwards almost abutting the thick centre of the mounting, so you couldn't ream it with a to and fro action. After stabbing down with a srewdriver, a piece of slightly bent coat hanger is best to ensure patency.
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Patency? Iii have to look that up sometime. Id think it would depend how flexible the wire was, but partial is likely better than nothing, and the veg oil would likely get all the way in. Academic for me anyway, but galvanised wire might also serve, and some of the galvanising get rubbed off on the disks.
I suppose another motivation for brake fluid flushes was that I found the old (coffee filtered) stuff quite useful as a decoke cleaner on carbs and, most recently, on my removed pistons, especially the ring grooves, which used up most of my stock
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In my case, corrosion inside a wheel cylinder caused it to leak.
The leakage caused a brake shoe liner to detach,
The brake shoe liner jammed in the brake drum and heated it up, which caused the saturated brake fluid to boil.
The bubbles in the brake fluid caused total brake failure.
A chain is as strong as its weakest link.
This system had been neglected for an unknown period, but almost certainly a lot longer than 2 years, so this failure does not specifically support a 2 year recommendation.
OTOH it certainly contra-indicates your "never" recommendation.
IIRC you run an old car long term so the "It'll be the next punters problem" jive doesn't necessarily apply
Edited by edlithgow on 22/08/2023 at 01:59
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In my case, corrosion inside a wheel cylinder caused it to leak.
At this stage, one would have thought remedial action would have been taken. My 1980 TR7 service record shows I changed the brake fluid in 1989. In 2000 at 59,000 miles I renewed the leaky o/s rear brake cylinder seals, replaced a contaminated shoe and renewed the brake fluid. In 2004 I serviced the o/s cylinder again to pass the MoT and in 2006 at 63,100 miles it got a new n/s shoe! (as with the o/s, only one needed replacing. Only in 2010 at 30yrs old and 65,000miles did I get my indy to replace the original brake cylinders and shoes which to date have only done fewer than 10k miles.
The leakage caused a brake shoe liner to detach,
The brake shoe liner jammed in the brake drum
Surely this would have been noticeable?
This system had been neglected
I don't neglect my system!
OTOH it certainly contra-indicates your "never" recommendation.
No it doesn't. The seized brake might well have caused even fresh fluid to boil!
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he leakage caused a brake shoe liner to detach,
The brake shoe liner jammed in the brake drum
Surely this would have been noticeable?
An unanswerable hypothetical.
It might have been noticable to someone with a higher level of awareness than me.
It probably would have been noticable if one had examined the brakes, or touched them.
The FACT, however, is that, negotiating Taiwanese city traffic, at night, I didn't notice it. No screechy noises, no serious level of drag. The brake fluid possibly acted to some extent as a lubricant.
If you make it a general recommendation that you dont need to change your brake fluid, ever, you have to allow for the possibility that some of the people who might believe you might not be driving gods, or very mechanically aware.
And anyway, SO WHAT if it would have been noticable?
It would still clearly be better for it not to have happened in the first place.
Best defense is no be there.
This system had been neglected
I don't neglect my system!
I didn't say you did, but now I will, since pretty much by definition, and by your own account, quite clearly you do, You just happen to have got away with it so far
OTOH it certainly contra-indicates your "never" recommendation.
No it doesn't. The seized brake might well have caused even fresh fluid to boil!
A contra-indication does not require absolute certainty. Its a balance of probability thing., but this gets rather close to absolute certainty.
Its very likely that the binding brake would not have happened without the corrosion caused by the ancient brake fluid. That corrosion was an observed fact.
Its certain that ancient brake fluid is more likely to boil than fresh fluid.
IF a brake can bind with fresh brake fluid, and IF this could cause fresh brake fluid to boil, ancient brake fluid would still be a BAD THING
Your denial of this comes rather close to denial of reality,
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If you make it a general recommendation that you dont need to change your brake fluid, ever, you have to allow for the possibility that some of the people who might believe you might not be driving gods, or very mechanically aware.
That is why I have never recommended that 'you don't need to change brake fluid,ever'. I merely mention what I personally do, don't do, would or would not do or have done (including my changing of brake fluid ...above!).
I don't neglect my system!
I didn't say you did, but now I will, since pretty much by definition, and by your own account, quite clearly you do, You just happen to have got away with it so far
Don't confuse masterly inactivity with neglect. (Many normal tonsils, appendixes and foreskins have been removed, courses of antibiotics prescribed and gallons of brake fluid wasted as a result of unmasterly overactivity).
Its certain that ancient brake fluid is more likely to boil than fresh fluid.......IF a brake can bind with fresh brake fluid, and IF this could cause fresh brake fluid to boil, ancient brake fluid would still be a BAD THING.......Your denial of this comes rather close to denial of reality,
But I don't deny this - apart from ancient brake fluid being a shouty BAD THING! Its boiling point and water content is just slightly less good than fresh fluid. All I am saying is that with modern braking systems, brake fluid is very unlikely to absorb significant quantities of water. Even if it does, it is also unlikely to get anywhere near hot enough to boil in normal driving circumstances, including the occasional high speed emergency stop.
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Yes I've noted your distinction between personal policy and advice before, and it is a valid point, if a bit of a semantic one, especially given that, IIRC, the OP up above says "Thanks for the advice".
Not your fault, of course.
As for the rest... All that reality defiance to save, what, a quid or two's worth of brake fluid?
Really?
Re the "modern braking systems" jive, your TR7 braking system is even older than mine is, so even if "modern braking systems" were significantly better in this regard (which I am aware of no evidence for) it doesn't really apply.
You aren't "advising" anyone who might have a "modern braking system". remember?
Anyway, words in the form of facts, a case study description, and economic rational argument having failed, perhaps a picture will fare better, though I'm not optimistic.
[url=servimg.com/view/18149521/220][img]i.servimg.com/u/f35/18/14/95/21/img_6925.jpg[/img][/url]
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If your position is that old wet brake fluid is "unlikely to get anywhere near hot enough to boil in normal driving " you might, at the risk of taking some casualties, be able to hold it for a while, but reality is likely to outflank you, since the corrosion caused by the old, wet brake fluid is likely to cause failures that mean that "normal driving" doesn't apply.
I dont seem to have a picture of the wheel cylinder involved in the total brake failure, which I replaced at the time along with the brake shoe, and extensive high pressure flushing of the system.
The top picture is the other wheel cylinder which failed about a year later. The corrosion presumably stops when you flush the system, but you don't get rid of its debris, which continues to cause wear.
The second picture is the sludge coated left front caliper piston which jammed up maybe a couple of years later, causing severe overheating, but no boiling. Stripped and cleaned. I did the other similarly sludgy one a bit later, before it got around to failing, Proactive or what?
I havn't done the master cylinder, because I couldn't get a seal kit for it, so thats likely lurking.
You could also, of course, and probably more commonly, get overheated brakes due to your calipers jamming, but I'd done them earlier, and it wasn't that.
I suppose you could normally drive using engine braking so you wouldnt need the brakes in normal driving. Better be careful though, since I assume you wont be wearing a seatbelt, since you dont crash in normal driving.
Edited by edlithgow on 24/08/2023 at 01:30
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In my case, corrosion inside a wheel cylinder caused it to leak.
At this stage, one would have thought remedial action would have been taken. My 1980 TR7 service record shows I changed the brake fluid in 1989. In 2000 at 59,000 miles I renewed the leaky o/s rear brake cylinder seals, replaced a contaminated shoe and renewed the brake fluid. In 2004 I serviced the o/s cylinder again to pass the MoT and in 2006 at 63,100 miles it got a new n/s shoe! (as with the o/s, only one needed replacing. Only in 2010 at 30yrs old and 65,000miles did I get my indy to replace the original brake cylinders and shoes which to date have only done fewer than 10k miles.
One would have thought right. As I said, I replaced the wheel cylinder and brake shoes, cleaned out the reservoir and bi-directionally pressure flushed the hydraulic system, changing it several times.
I later learned that this wasn't enough, and that it needed both calipers to be completely stripped and cleaned, removing the pistons. I should probably have completely stripped and cleaned the master cylinder as well, but didn't want to risk trying that without a seal kit
Re your service history, doesn't sound much like "masterly inactivity". Sounds like "reactive maintenance" (AKA "remedial action"), as opposed to "preventative maintenance"
Best defense is no be there.
It doesn't really support never changing your fluid, since AFAICT you changed or refreshed it it at 9, 11, 4, 2 and 4 year intervals in response to failures that might well have been due to the fluid having been left too long.
I dont know how long my fluid was left. Since the damage was extensive, it could have been longer.
Edited by edlithgow on 25/08/2023 at 08:32
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I also consider two years too soon and five is a good compromise unless arduous driving conditions such as towing perhaps. You will get a range of views from do it now to leave it until the car is sold.
The problem is that it then makes the supposed '6 year' servicing cycle from Mazda (and I suspect many other makes do this) incredibly expensive, given that on the older models, it still includes the once-every-two years changeout included in the price, which for my 17yo Mazda3 petrol is around the same, possibly even a bit less.
If all these 'manufacturer' services are is glorified 'minor' and major' services, sans all fluid and filter changes except the oil, then in my view they should be far cheaper, as most items on a service other than them are checks, not parts replacements, and where the work takes 2 hours, tops, often well under that.
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If your car's brakes feel 'right' under all conditions, if it ain't broke, probably don't fix it.
My brakes "felt right" right up until I suddenly couldn't feel them at all.
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If your car's brakes feel 'right' under all conditions, if it ain't broke, probably don't fix it.
My brakes "felt right" right up until I suddenly couldn't feel them at all.
That might depend on whether you can remember how they felt a year ago, rather than how they felt yesterday ?
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If your car's brakes feel 'right' under all conditions, if it ain't broke, probably don't fix it.
My brakes "felt right" right up until I suddenly couldn't feel them at all.
That might depend on whether you can remember how they felt a year ago, rather than how they felt yesterday ?
Uh?
Perhaps you mean one might not notice a gradual deterioration?
This wasn't a gradual deterioration. It was a sudden cessation of function. As above
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Some regulars on here see little advantage in frequent changes of brake fluid, unless there is reason to suppose that it has been degraded by absorbing moisture (which in the old days could lead to boiling during continuous braking, and brake fade).
"in the old days"?
Brake fluid "degraded by absorbing moisture " is going to boil under continuous braking, old days, new days, dog days, salad days.
It COULD be that modern brake systems are better sealed, though I'm aware of no evidence for that.
I am aware of evidence that modern cars are more powerful, so modern brake systems have to dissipate more energy.
In any case, you dont need reason to suppose that it has been degraded by absorbing moisture to justify changting it.
You do, however, need reason to suppose it could NOT be degraded by absorbing moisture to justify never changing it, and that can;t be done
(EDIT: Unless I suppose, you monitor your brake fluid moisture content with a known-to-be- accurate method, and it stays at a level which is known to cause no corrosion and does not significantly lower its boiling point.)
Edited by edlithgow on 24/08/2023 at 01:48
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