Brake fluid

[PaulAA]

I may have discovered a new way of harnessing free energy. Forget wave, wind and solar - I think my recent experience will generate enough sage nodding of heads amongst you chaps to power a small provincial town.

 

A couple of months ago, whilst my '6 was enjoying a rest between periods of good weather, my brake master cylinder failed and incontinently emptied its contents over the servo and garage floor. With a reckless disregard for life and limb, I managed to get the brakeless car to a local workshop, with my wife galantly walking ten paces ahead brandishing a red sweater.

 

Now, the PO, having skimped on more important areas, had lavishly embellished the car with silicon brake fluid and I shared the empty packaging with the mechanic. DOT 5 - nothing else, please. Two days later, new master cylinder installed, I drove away a happy man, having been presented with the remains of the new fluid with which the system had been topped up. Proud as punch, my man tells me that he's gone one better and (let the nodding commence) used DOT 5.1.

 

So now my '6 is enjoying another sojourn in a different workshop, having the system flushed. Two months of enthusiastic pedal pumping has pushed enough silicone/glycerin mix past the befuddled seals to wholly ruin brake shoes, drums and, likely as not, the rather shiny and new replacement brake cylinder. The jury is still out on the front calliper seals.

 

So, now I know that DOT 3, 4 and 5.1 are glycerin-based and only DOT 5 is silicone. Unlike my ex-mechanic.

 

Sometimes, a bit of German order in classification would help save Schwachsinnige like me from our own stupidity.

 

Cheers

 

Paul

[Lebro]

My neck hurts now.

 

Bob.

[Steves_TR6]

people do that sage nodding thing every time they see the 'Automec' triangular labels .......

[Peter Cobbold]

Send the ex-mechanic the bill. And he can pass it on to the idiots at DOT, who can one presumes only count up to 5.

For once it is not a EU cock-up.

[PaulAA]

Send the ex-mechanic the bill. And he can pass it on to the idiots at DOT, who can one presumes only count up to 5.

For once it is not a EU cock-up.

 

Peter

 

I decided to put it down to experience - he's an old guy, tried his best, intended no malice, etc., etc. and is, I imagine, an absolute whizz with forty year old Fiat 125s, 126s and Ladas. Just not TRs. I'd rather send the bill to the PO for missing important things and wasting money on silicone brake fluid (which I still can't scrape off the epoxy finish on the garage floor).

 

Cheers

 

Paul

[Peter Cobbold]

Hi Paul, I have used silicone for 25 years, and it works fine for me. The 6 stood under a leaking tarp on a Wales hillside for two winters and the brakes were not affected. With glycol the car woulld have been immobilised with solid-seized brakes. I now have a very slow leak somewhere under really heavy braking, but after 25 years I cant blame that on the fluid.

Peter

 

edit: Paul, I swapped to silicone as part of a total brake rebuild - new seals, new hoses, wheel cylinders, pipes, m/cyl - the lot. I am unsure how you should best proceed with getting rid of the fluid mixture. It has to be thorough. Peter

Edited October 8, 2014 by Peter Cobbold

[Fireman049]

When I fitted Coopercraft four pot calipers to my 1965 'E'-type Jaguar the instructions clearly stated that

Silicon brake fluid should not be used?

Why is this I wonder?

 

Tom.

[Peter Cobbold]

When I fitted Coopercraft four pot calipers to my 1965 'E'-type Jaguar the instructions clearly stated that

Silicon brake fluid should not be used?

Why is this I wonder?

 

Tom.

Tom,

Your answer might be in here somewhere:

http://www.mossmotors.com/SiteGraphics/Pages/Brake_Fluid/brake_fluid_long.html

 

Maybe this?:

""Because of the dissolved air, silicone fluids are up to three times more compressible than glycol based fluids. This can contribute to a slightly spongy feeling brake pedal, particularly near the higher end of their temperature range but well below the dry boiling point. While this is of absolutely no consequence for normal street use, this is why silicone fluids are not used in race cars. A spongy pedal makes it difficult to modulate the brake pressure under racing conditions.""

 

Or perhaps Coopercraft found water pooling in their calipers ?:

"Since silicone will “float on top of the water”, the tiny amount of water logically will in time work is way down to the lowest points in the system. In theory, if that low spot is the caliper, the water can boil at 212° F, well below the dry or the wet boiling point"

 

 

Peter

Edited October 8, 2014 by Peter Cobbold

[Fireman049]

Many thanks Peter ~

 

Tom.

[stuart]

Coopercraft were covering their a**es same as most suppliers of brake parts. AP Lockheed state similar as in warranty void if Silicon fluid used.

Stuart.

[Geko]

and that ".1" thing sounds pretty much like the programmed obsolescence of 5.0

[RogerH]

I read a USA motorbike club report on SBF (I think it could have been Harleys).

The problems they had was on rough roads and off road conditions.

The vibration over prolonged periods caused the SBF to aerate both in the master cylinder and the pipe runs.

This caused the brakes to be very very bad.

 

Normal DOT4 is much less affected by aeration.

 

The only benefit of SBF is that it does not attack the paintwork - neither does an anchor; but that is not a good enough reason for using it.

 

Roger

[ctc77965o]

Silicone (not Silicon)

The negatives:

1)sponginess and high gas solubility.

2) immiscibility with water means that any water migrates to the lowest point where it can't be bled out and causes corrosion and loss of brakes at 100c, open bonnet in rain and water will get in.

3) if you have a servo and it suffers an internal failure the silicone will get sucked into the engine and destroy it by being burnt to form sand in combustion chambers.

 

Positives:

1) it's not hygroscopic so it doesn't 'suck up' water. Meaning it's great for stored vehicles.

2) it has a very high flash point meaning it won't start a fire when splashed on a hot exhaust in an accident (Dot 3/4/5.1 will).

3) it doesn't damage paint

 

Nothing is perfect....maybe DOT6.1.1 will be the best of both worlds....

[cbxman]

I have used SBF in my Honda CBX for the last 12 years. It is a fit and forget product perfectly suited to low mileage classics. When I was investigating this product I was informed that Japanese brake systems were fine with silicone, but not to use it with Italian brake systems, typically Brembo, as the rubber used in their seals is not compatible.

 

Certainly, on a motorcycle, when a master cylinder seal fails, DOT4 can wreak havoc with the paintwork on a petrol tank. Silicone just polishes off. Having said that the MC seals have never failed since I changed silicone, however I have spilled silicone whilst filling it up......

 

I wonder whether some of the confusion over suitability arises from the mixed compatibility of different brake manufacturers.

 

Maybe one of our forum chemists can shed some light?

[PaulAA]

Silicone (not Silicon)

The negatives:

1)sponginess and high gas solubility.

2) immiscibility with water means that any water migrates to the lowest point where it can't be bled out and causes corrosion and loss of brakes at 100c, open bonnet in rain and water will get in.

3) if you have a servo and it suffers an internal failure the silicone will get sucked into the engine and destroy it by being burnt to form sand in combustion chambers.

 

Positives:

1) it's not hygroscopic so it doesn't 'suck up' water. Meaning it's great for stored vehicles.

2) it has a very high flash point meaning it won't start a fire when splashed on a hot exhaust in an accident (Dot 3/4/5.1 will).

3) it doesn't damage paint

 

Nothing is perfect....maybe DOT6.1.1 will be the best of both worlds....

 

I think you have overlooked three other negatives to silicone (not silicon):

 

- it is expensive at c. 10x the cost of DOT 5.1

- when spilt/leaked, it is the devil's love-child to get rid of

- it is easily contaminated by the ill-informed within the mechanic fraternity (I have discovered, to my cost)

[Peter Cobbold]

 

 

I think you have overlooked three other negatives to silicone (not silicon):

 

- it is expensive at c. 10x the cost of DOT 5.1

-

It is not expensive if glycol fluid is changed as often as it should be, which is every year or so depending upon how wet/humid the environment.

Edited October 9, 2014 by Peter Cobbold

[TorontoTim]

Certainly, on a motorcycle, when a master cylinder seal fails, DOT4 can wreak havoc with the paintwork on a petrol tank.

What are these newfangled hydraulic motorcycle brakes of which you speak? (Says the '65 Norton rider)

[stuart]

 

It is not expensive if glycol fluid is changed as often as it should be, which is every year or so depending upon how wet/humid the environment.

3 years normally.

Stuart.

[cbxman]

Tim,

 

I appreciate that news travels slowly to the colonies, but I didn't think it was that bad!

[McMuttley]

"Brake fluid" you mean there is more fluid i need to service !

 

Not in my car, the pedal travel of 5mm max' shows that i have pure graphite in my pipes !

[Alec Pringle]

Last week I was looking at a lovely '50s Cresta that had suffered from a SBF saga. Low mileage, high days and holidays sort of a car.

 

Some few years back, a well meaning 'classic specialist' had drained the glycol fluid and replaced with silicone - simple as that, no seal change or whatever. Couple of years down the line, an emergency stop didn't, with resulting collateral damage. The seals had gone. Bright assessor inspected closely, the insurer refused the claim, inappropriate hydraulic fluid, end of discussion. 'Classic specialist' had demised in the interim, very expensive learning curve for the owner.

 

Next chapter, the car was rebuilt with hydraulics flushed, nos hydraulic seals, and SBF. That lasted a couple of years before the seals went, en route to the annual MoT, fortunately with only minor cosmetic damage resulting. There are no new repro seals for this model, the nos items proved not to be SBF compatible. This time the owner, understandably, didn't bother troubling the insurer. More learning curve, not quite so expensive this time.

 

Next instalment, strip and flush hydraulics and replace seals with more nos items, refill with glycol, again at considerable expense. That lasted a year. Ever tried flushing out SBF residue ? Hiding to nothing, you can't shift the last of the damn stuff, so the seals protest in due course. Another wallot walloper moving up the aforementioned curve.

 

This year's solution . . . . tear down the brake and clutch systems, renew cylinders on all 4 drums, and the master, and the servo, and all pipework, and all shoes. Then renew clutch master and slave, pipework, and clutch. Finally, with all that replaced, refill with Dot 3 as per the original design spec.

 

Fingers crossed it works for the poor blighter. I'm sure it will, it's back as GM intended. Meanwhile, the cost of several sets of unobtainium nos Vauxhall parts would make any TR man's eyes water.

 

Of course silicone brake fluid can work, and many folks are more than happy with it - but you do have to regard a change from glycol to silicone, or vice versa, as a complete tear down and replace exercise . . . . to my way of thinking it simply is not worth the risk with seals that are not warranted for SBF.

 

Cheers

 

Alec

Edited October 9, 2014 by Alec Pringle

[Peter Cobbold]

I agree with Alec,complete strip down.

====

But its far from obvious why.

The test protocol for fluids is FMVSS116

The SiliconeBF I use meets the US standard FMVSS116.

http://www.namrick.co.uk/acatalog/Home_Silicone_Brake_Fluid__Approved_To_FMVSS_116_Dot_5_139.html

That test protocol involves testing rubber brake cups in brake fluids, whether glycol of silicone,

All brake fluids are put through this test:

""The standard applies to all fluid for use in hydraulic brake systems of passenger cars, multipurpose passenger vehicles, trucks, buses, trailers, and motorcycles which are equipped with a hydraulic brake system.""

www.nhtsa.gov/DOT/NHTSA/Vehicle%20Safety/.../TP-116-04.pdf

(section 6.11 starting p27 of pdf)

So: either UK brake rubbers dont meet this standard. In which case we could source compliant items from USA. Or perhaps Moss etc can confirm that UK brake rubbers are compatible with break fluids meeting FMVS116. In which case they are safe for any glycol or silicone fluid....but theres a snag:

The test says nothing about exposing rubber seals to first one fluid type then another. I suppose it is possible that swelling caused by one fluid, say glycol, is different chemically from the other, silicone. If swelling in one were added to extra swelling- or shrinking - in another then there's the problem. Note that some swelling is mandated by the test. Or hardening might be greater.

That's why I am inclined to go for the complete strip down approach. Not good news for PaulAA.

 

 

 

Peter

Edited October 11, 2014 by Peter Cobbold

[Andy Moltu]

Interestingly the blurb with Silicone brake fluid says it is compatible with DOT 4 although I suspect, as Pete says, no formal testing of rubber components being exposed to both has been done.

 

My experience with silicone is that it works fine if you are diligent about bleeding your brakes to get the air out properly.

Concerns about water (from condensation in the master cylinder) pooling in the calipers are probably valid. I guess getting the brakes hot and bleeding them before they cool would get rid of that as steam.

 

The flip side is that, in my experience, I have boiled the brake fluid in the Alps, making me wonder if it boils at a significantly lower pressure at altitude.

Things to consider include that I was using Tarox discs and Hawke pads which may generate more heat and possibly transfer more of that heat through the pads to the caliper than standard disc and pads. Currently have fitted an ECB vented caliper kit - with spaced standard calipers and Mintex pads (didn't have any confidence with the Greenstuff pads that came with the kit) but may be some time before I get to the mountains to test my theory.

[Rodbr]

I agree with Alec that total strip down and replace is the only option when changing the fluid.

Depending on your outlook I was either lucky or unlucky. My car came from the US with all new brake components and filled with SB, it then sat for 20 years in a garage unused.

As part of the rebuild I replaced all the new but externally rusty pipework. I stripped all parts down to find they were like new internally. I replaced all pipework and rebuilt the system and used fresh SBF.

I read all the information and reasoned that rather than take a single risk I would use what had always been in the system namely Automec SBF. It occurred to me that all parts were either US made or US| REBUILT and they typically use SBF.

After initial adjustment pedal box issues I have not had a single problem. The pedal is firm, I have had no issue after layup but that isn't usually long between runs.

 

WOULD I DO it again ? The jury is out and if I were to change the calipers and discs for later 4a ones I would probably rip everything brake/related. The downside being that any external contamination is there for keeps and virtually impossible to remove from paintwork even by blasting.

 

Any tips on how to remove SBF contamination would be of great interest to me and probably others.

AN INTERESTING ARTICLE

http://www.mossmotors.com/SiteGraphics/Pages/Brake_Fluid/brake_fluid_long.html

 

Warning: which I don't seem to have seen mentioned about using SBF with a servo. In the event of a servo malfunction and fluid gets drawn into the engine it is extremely bad for it and potentially terminal as:

"Silicone, when sucked through a leaking vacuum booster into an engine, burns to form silica sand and quickly wears down an engine's internal parts. Glycol burns harmlessly." just large quantities of white smoke like choosing a new Pope!

Edited October 10, 2014 by Rodbr

[stillp]

open bonnet in rain and water will get in.

 

Don't you have a lid on your master cylinder?