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Fireman049

Brake/Clutch Fluid?

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I've renewed everything on my brake and clutch systems. New discs, calipers, copper brake pipes

and flexible s/s pipes. Which brake fluid should I use?

 

When I fitted 'Coopercraft' four cylinder front brake calipers to my 1965 'E'-type Jaguar I was instructed NOT to use Silicon

brake fluid ~ Why???

 

Tom.

Edited by Fireman049

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Hi Tom,

 

the principle concern with SBF is compatibility of flexible seals and tubes within the system, as in are they potentially subject to long term deterioration.

 

International agreements call for vehicle braking systems to be compatible with the American DOT standards, which is fine and logical. SBF is DOT 5 category. The majority of manufacturers employing glycol and/or boron ester based fluids - DOT 3, DOT 4, DOT 4 Super, DOT 5.1 - do not seem to wish to include DOT 5 (SBF) amongst their recommendations.

 

I do not accept the frequent cynical suggestions that this is simply because the brake manufacturing industry wants to sell more fluid, as in SBF has a much longer potential working life than traditional fluids.

 

Often overlooked, the fact that water is absorbed into a traditional fluid and reduces its performance accordingly, whereas in an SBF system any water introduced will not be absorbed but find its way to the lowest point, which if it happens to be a hot calliper or cylinder can have catastrophic result as the water boils under braking . . . . . and braking promptly disappears in a puff of steam . . . .

 

There is no doubt in my mind, and I've undertaken a lot of research on this over 40 years, that SBF can and does attack at least some types of hydraulic seal materials in regular use for braking systems. Other types of flexible seals and hoses seem to be unaffected.

 

If I am using SBF (and I do for hydraulic clutches) then I have to be certain that the system is SBF compatible. If it proves otherwise, not the end of the world, I can drive without a clutch if I have to.

 

Braking systems are another matter entirely . . . . . .

 

It can be extremely difficult, often impossible, to obtain any sort of confirmation, let alone guarantee, from equipment manufacturers or suppliers that a particular hydraulic component is in fact SBF compatible. Without that reassurance, I simply wouldn't use SBF with that component. Brake failure kills people. Period.

 

For an E-type system I'd suggest that a DOT 4 Super specification fluid is the answer, high boiling points wet and dry and relatively low rate of water absorption) but make sure it is compatible also with DOT 3, the original Jaguar spec, as some of the DOT 4 Super brands are not retro compatible with DOT 3.

 

As a generalisation, for road applications (as opposed to competition) I always look to a brake equipment manufacturer's own fluid, or possibly one from a lubricant manufacturer . . . . as opposed to vehicle manufacturer or proprietary branded hydraulic fluids. Yes, the former probably will cost more. You get what you pay for . . . . . I spent some past years in motor factoring, with access to confidential technical specs, hence my comments.

 

Cheers

 

Alec

Edited by Alec Pringle

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...and follow the maker's recommendation to change the fluid periodically - my eurobox requires it to be done every 2 years as part of the service schedule, and cost under 50 quid at a main dealer. - I've just had it done and it was cheaper than having the a/c recharged.

Peter W

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Hello Alec,

 

You said, “…water is absorbed into a traditional fluid…”

 

I’ve read this many times over the past 45 years of working on cars, and I’m sure it is true.

 

Recently though I’ve been wondering “How?”

 

A car hydraulic system is sealed. If it weren’t then all the brake fluid would run out.

So if the brake fluid cannot run out, how can the water get in?

 

The only place that the system can be open to the atmosphere is the master cylinder reservoir, and even that has a cap on it (OK, with a very small hole in it.)

 

I’m intrigued to know the answer.

 

 

Charlie D.

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Via the venting system, the reservoir cap . . . . . we're only talking tiny amounts of water to drastically reduce the boiling point of conventional hydraulic fluids - or to create micro-droplets of water within SBF filled systems.

 

And no, there is no effective way of eliminating water absorption.

 

Do bear in mind that SBF was originally created not as a hydraulic brake fluid for running road vehicles, but as a fluid to preserve the numerous hydraulic systems within military vehicles under long term storage in low-humidity desert establishments in the USA . . . . .

 

Cheers

 

Alec

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About halfway down this page [ http://bullfire.net/TR6/TR6-76/TR6-76.html ] is a some logic supporting the use of DOT5 fluid in a TR6 where the master cylinder mfr warned against it. It includes an excerpt from the US federal DOT (Department of Transportation) regulation regarding brake fluid:

 

"Brake fluid means a liquid designed for use in a motor vehicle hydraulic brake system in which it will contact elastomeric components made of styrene and butadiene rubber (SBR), ethylene and propylene rubber (EPR), polychloroprene (CR) brake hose inner tube stock or natural rubber (NR)." [49 CFR 571.116]

 

DOT5 fluid appears to be superior to DOT3/4 In just about every important respect save one: air entrainment. This is reportedly not a problem for most driving conditions save racing, and is likely why DOT5 is not recommended for most ABS brake systems.

 

Ed

Edited by ed_h

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About halfway down this page [ http://bullfire.net/TR6/TR6-76/TR6-76.html ] is a some logic supporting the use of DOT5 fluid in a TR6 where the master cylinder mfr warned against it. It includes an excerpt from the US federal DOT (Department of Transportation) regulation regarding brake fluid:

 

"Brake fluid means a liquid designed for use in a motor vehicle hydraulic brake system in which it will contact elastomeric components made of styrene and butadiene rubber (SBR), ethylene and propylene rubber (EPR), polychloroprene (CR) brake hose inner tube stock or natural rubber (NR)." [49 CFR 571.116]

 

DOT5 fluid appears to be superior to DOT3/4 In just about every important respect save one: air entrainment. This is reportedly not a problem for most driving conditions save racing, and is likely why DOT5 is not recommended for most ABS brake systems.

 

Ed

USA specs are different to UK/Euro specs, as stated above by Alec the SBF was developed for USMC to long term store vehicles in the desert not as a road going vehicle brake fluid.

We can and have had this argument since it appeared on the market in the USA and then found its way over here.

If it was universally approved for the road then why doesnt every manufacturer of vehicles use it in their cars regardless of ABS fitment (clutch systems)?

Stuart.

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Sorry Ed, but the statement " DOT5 fluid appears to be superior to DOT3/4 In just about every important respect save one: air entrainment." is quite simply arrant nonsense.

 

I first started perusing USA Triumph websites back in 1998, it seemed at the time that an awful lot of what was being published owed more to misplaced enthusiasm and personal opinion than established fact.

 

Subsequent years did little to change my thoughts - occasional attempts to offer polite observation to American authors proved fruitless . . . . But then a guy who can publish opinion without an adequate knowledge basis probably isn't that interested in first-hand experience here in the UK, any more than he's interested in the considered views of OE component manufacturers. Maybe internet minor celebrity status counts for more ?

 

Bullsh*t baffles brains. Bullfire may well be an approximate translation ?

 

SBF has bling factor, and it doesn't damage paint in the same way that traditional hydraulic fluids can do, no argument there. In my experience it has prove quite satisfactory in clutch systems, which is where I'm happy to use it, in conjunction with component rated for exposure to SBF. In terms of braking systems however, I have first hand experience of 40 years of a considerable number of serious problems arising from the use of SBF.

 

I would not even consider utilising SBF as a brake fluid without a copper-bottomed confirmation of suitability for every last component of the braking system, and even then I would only consider it for employment in cars of relatively modest capability which are unlikely to be driven in such a manner as to occasionally require every last ounce of available braking effort and driver reaction speed. If you understand the limitations of SBF then the logic behind that view will be self-evident.

 

A TR, any TR, is a sports car. I suggest it is reasonable to expect that from time to time a TR will require all of its braking abilities, and sometimes more . . . . That in itself is sufficient for me to wish to stick with a top-class Dot 4 Super formulation, and to change it every 2 years, and be damned to the cost and time of doing so.

 

I really don't wish to be the TR guy who flattened someone's little grandchild because he skimped on his brakes and felt that 95% was good enough.

 

Cheers,

 

Alec

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It's interesting that this topic can be so polarizing.

 

My interest in Dot 5 was pretty much totally based on the fact that is doesn't attack paint. This was enough to seal the deal for me, provided there wasn't some negative offsetting factor. In my research, I found that, compared to DOT3/4, Dot 5 has: a higher dry boiling point, a higher wet boiling point, lower viscosity, and lower hygroscopicity.

 

DOT 5 does have higher compressibility, which varies with temperature and entrained air. After some investigation of that point, I concluded to my satisfaction that the higher compressibility would be a small factor in a well setup TR6 braking system in street use.

 

Obviously, others seeing the same facts may come to other personal conclusions.

 

Ed

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The reason DOT 5 is not used currently in cars with ABS is because the ABS modulator would need recalibration. By the same token a DOT 5 ABS system could not use a DOT 4.

 

I still use Lockheed 22.....left over from when we got rid of the DH Comets!

Castrol aero 35 works quite well but Skydrol is a definite no....Coz it stings like hell if it gets in your eyes and it’s the bestest paint stripper you will ever come across!

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why doesnt every manufacturer of vehicles use it in their cars regardless of ABS fitment (clutch systems)?

 

Stuart, it costs more, and offers little or no advantage for a vehicle manufacturer, with the possible disadvantage of warranty claims for a soft pedal.

 

Pete

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The oft-quoted 'wet' boiling point of SBF is a chimera . . . . . SBF is hydrophobic, it does not absorb water, therefore cannot have a 'wet' boiling point. As noted previously, this tends to limit water ingress to the vent system, whereas hygroscopic fluids will also tend to absorb by diffusion through hoses, for example.

 

The 3.7% water content of 'semi-saturated' glycol/ester based fluids is that from which the 'wet' boiling point is derived. 3.7% of free water sloshing about in an SBF system is likely to accumulate and produce localised corrosion, apart from boiling at 212F/100C.

 

I base my own views not just on internet 'facts', nor on manufacturer's data, but also from the experience of having seen in service garage / MOT bay situations dozens of problems of one sort or another which appear to have resulted from the use of SBF - in some instances, very much potential safety critical problems.

 

The odd underbonnet paint loss is neither here nor there in my book, irrelevant compared to losing even a fraction of potential braking ability when it's needed most.

 

Edit - this is the USA site I was trying to recall earlier - more accurate than most in terms of data content

 

https://www.lelandwest.com/brake-fluid-comparison-chart.cfm

 

Cheers,

 

Alec

Edited by Alec Pringle

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The odd underbonnet paint loss is neither here nor there in my book, irrelevant compared to losing even a fraction of potential braking ability when it's needed most.

 

 

Cheers,

 

Alec

And this is the nub of the issue. When cars are being restored to better than new condition and polished to within an inch of their life, a shiny engine bay is important.

 

I decided to opt for DOT 4 in my completely rebuilt TR3a and have since had a couple of brake fluid incidents that have made a mess of my under bonnet bling. fortunately, I'm not too bothered by the under bonnet appearance as long as it's relatively clean.

 

Rgds Ian

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From a slightly different angle....Many years ago, it was considered safe to use SBF in old Japanese motorcycles, but not Italian ones as the the SBF would attack their rubber. I am pleased to say that my Honda CBX which is now 38 years old has had SBF in it for the last 17 years. I have not had to touch the brake system for 17 years, other than a top up to compensate for pad wear. I did get used to the slightly softer brake lever, but there was never any doubt that the brakes couldn't deal with any spirited riding! Of course on a motorcycle the position of the master cylinder above your beautiful petrol tank is more of a cause for concern.

 

Cheers,

Jerry

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Hhhhmmmmmmm Honda CBX the poster bike I always lusted after.

Luck man Jerry.

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Hhhhmmmmmmm Honda CBX the poster bike I always lusted after.

Luck man Jerry.

Not being a biker I just googled the CBX - wow, what an engine.

 

Now if only I had my old Bond Mk F to stick one of those into.

 

Roger

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Hamish

 

If I remember they cost circa £2,750 in 1978, so most people bought the Suzuki GS1000 instead as it was only £1800. The GS was only very slightly slower, but the CBX was the jaw dropper....and still is. I nut and bolt restored mine and it goes "in the box" with me!....well if you know what I mean!

 

 

Roger

 

The Suzuki Hyabusa 1300 engine is the motor of choice for most small hot car builders. CBX is too pretty to put under a bonnet!

 

Many motorcycles when dragged out their slumber in the shed over winter are likely to have a seized brake, but none of that nonsense with SBF.

 

If I was confident that it wouldn't attack TR4A rubber, then I would go the same way again. It really is a great solution for sedentary vehicles.

 

I know.... I should rag it every day, but with all my vehicles and a motorhome, which I like to use, there isn't much time to give much attention to any one vehicle.

 

Too many toys :rolleyes:

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OMG Roger I’d never admit to owning one of them. Mind you replacing the Villiers 2 stroke with a CBX motor or better still a Hayabusa would give everything else on the road a bit of a shock......now there’s a thought.

 

Can carry on the argument of dot 1 to 10 versus silicone now.

I’m sticking with SBF and haven’t yet experienced any negative effects.

One thing I’m certain it would have been banned or withdrawn by the government if it had been dangerous!

Oh and talking to one of the chaps in Halfords they removed it from the shelf due to people topping up their brake/ clutch with silicone thinking it would be an improvement..... people don’t read the labels!

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I have used SBF in my TR6 for the about 20 years with absolutely no problem, the only thing I do differently is every couple of years I drain some of the fluid from each bleed valve to hopefully remove any water that has got into the system.

When going abroad with the car I do take a bottle of SBF as I could see problems getting it in say rural France if there is troubles with the hydraulics.

 

George

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I'm intrigued by the comments that SBF can attack some elastomer brake components. My understanding is that it is mostly silicone oil. Silicone grease - the oil with an inert filler - is commonly used as an assembly aid for O-rings and other elastomeric seals because it's benign towards these materials.

 

I had always assumed that problems with SBF attacking brake seals was due to these having previously "seen" DOT4 type fluids, which is understandable.

 

So, why should SBF attack some elastomeric brake components? Are the manufacturers using materials which don't like the silicone oil? Or is there an SBF additive which behaves aggressively towards some of these elastomers? I would be most interested if someone happened to know the answer.

 

Cheers, Richard

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Some 15 years ago I replaced my DOT 4 by SBF(purple color, but I forgot the make).

The car was restored 2 years before, all new seals/hoses, but a friend talked me into SBF.

The label on the SBF bottle stated it could be done by simply thorough flushing the system with the new SBF, no replacement of seals or hoses was required.

During changing the fluid, I noticed they did not mix.

After I drove the car with SBF for some time, my brakes seized, it appeared that the very tiny hole in the master cylinder that releases fluid back to the reservoir when the brakes are not applied was plugged.

I then took the entire system apart, thoroughly cleaned it replaced al seals and hoses, and filled with DOT4.

I am currently restoring my TR, all hoses and seals are new. I would like to use SBF, but am not sure I will not have issues with compatibility, so will stick with DOT4.

Annual replacement of the brake fluid, just a few strokes of the master cylinder per wheel until clear fluid drains out, is what I am used to do to avoid corrosion. Especially the fluid drained from the rear wheel cylinders can be dark.

Regards,

Waldi

Edited by Waldi

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I have used SBF in my TR6 for the about 20 years with absolutely no problem, the only thing I do differently is every couple of years I drain some of the fluid from each bleed valve to hopefully remove any water that has got into the system.

When going abroad with the car I do take a bottle of SBF as I could see problems getting it in say rural France if there is troubles with the hydraulics.

 

George

Thats a waste of time Im afraid as the water will accumulate at the bottom of the cylinders and the bleed nipples are at the top.

Stuart.

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I have had the clutch slave cylinder fail due to water settling in the bottom of it with SBF so I believe it is still a good idea to change your brake fluid periodicaly whatever fluid you choose to use.

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Thats a waste of time Im afraid as the water will accumulate at the bottom of the cylinders and the bleed nipples are at the top.

Stuart.

 

The solution is to get the brakes so hot that any water in the caliper boils and bleed them at that point.

25 Years of using SBF in the 6 the only problems I have experienced is boiling the fluid at altitude when driving hard on mountain passes. When this happened the fluid had been in the car for quite a few years, presumably long enough for enough water vapour to condense in the master cylinder and migrate to the calipers.

Bar that the only draw back is it is harder to bleed when refilling from empty.

The solution is to remove the calipers and drain all the fluid from them.

 

Beyond that DOT 5 meets/exceeds the DOT 4 specifications (if any label can be trusted).

 

 

In an emergency Dot 4 and 5 can be mixed but you loose the benefits (of either) and suffer the deficiencies of both.

 

There are reasons ABS cars have specific fluid requirements but not relevant to the TRs. DOT 5.1 is a different specification again.

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