New Brake Master - says no silicon!

[colin3511]

Hi,

 

I have a new brake master and it states on the box that if you use silicon brake fluid, the warranty is void. Does anybody know why this would be the case, as I assumed that silicon would be less harmful to the seals?

 

Thanks,

 

Colin

[Fireman049]

Hi Colin ~

 

When I fitted 'Coopercraft' four piston calipers to my 1965 'E'- type Jaguar I was told not to use Silicon brake fluid.

I'll never know why??

 

Tom.

[HSM]

A.P.Lockheed do not recommend silicone brake fluid due to its higher wear rate

 

 

Harvey S. Maitland

[Fireman049]

Thanks for that Harvey ~

 

Tom.

[RogerH]

Hi Colin,

the seals are designed for the standard DOT 4 Ethylene Glycol.

The silicone DOT 5 has no effect on them and so they should work. (DO NOT USE MINERAL OIL)

 

However as mentioned above the OEM's feel that the DOT 4 works better - I'm sure they have tested DOT 5 but appear not to like it.

 

Lets face it - DOT 5 was designed for long term storage of US military trucks and then work 20 years later. Would you expect it to be better than DOT4.

 

Roger

[stuart]

All AP Lockheed cylinders have this warning on them for the reason that they cannot guarantee the seals if you use Silicon fluid. Most people on here know that we neither use nor recommend Silicon for the same reasons.

Stuart.

[mike3739]

I have used Silicon for the past sixteen years & over 40,000 miles with no issues.

 

 

Cheers

 

Mike

[RogerH]

I have used Silicon for the past sixteen years & over 40,000 miles with no issues.

 

 

Cheers

 

Mike

Hi Mike,

quite right, but the OEM will not help you if you have a serious issue.

They say no - you ignore them.

 

I know that DOT4 will attack the paint, but so will brick walls and other traffic 'if' the brakes go tits upwards.

 

Roger

[Nigel Triumph]

I have used Silicon for the past sixteen years & over 40,000 miles with no issues.

 

 

Cheers

 

Mike

Same with me. Both TR6 and GT6 have been fine with silicone fluid for 12 years and 18 years respectively.

 

 

Nigel

[Yellowperil]

I've used silicon last 7 years with no problem.

 

Mine was put in by a reputable TR Specialised when I bought the car from him.

[ed_h]

My last TRW master cylinder warned to use ONLY DOT3 fluid on the reservoir cap. The packaging and instruction sheet that came with it said to use ONLY DOT4 fluid.

 

It was a little hard to take ether one seriously, so I used DOT5.

 

Whenever this comes up on one of these forums, the anecdotal evidence usually seems to heavily favor DOT5.

 

Just sayin'.

 

Ed

[Mike C]

Last time I looked the evidence was heavily against DOT 5. I'm sticking to DOT 4 .

 

Modern grades of DOT 4 seem to have overcome the moisture problem it had 30-40 years ago and I don't like ignoring Triumph's/ manufacturer's recommendations on rubber compatibilities.

[ed_h]

Last time I looked the evidence was heavily against DOT 5.

Looked where, Mike?

 

Ed

[Mike C]

This forum plus other British and Australian Triumph/British car forums/Moss newsletters , but it might have been 10-15 years ago now, when I did a lot of work on the brakes.

 

DOT 5 had two problems at the time- lack of brake feel/spongy operation and it was a one way street -once brake systems were converted over to DOT5 it was a major exercise to change back to DOT 4.

 

The general banter at the time was enough to convince me to keep using higher end DOT 4 fluid.

[Tim D.]

Also used silicone on all my old cars for 15 years. Seems ok.

[RogerH]

My last TRW master cylinder warned to use ONLY DOT3 fluid on the reservoir cap. The packaging and instruction sheet that came with it said to use ONLY DOT4 fluid.

 

It was a little hard to take ether one seriously, so I used DOT5.

 

Whenever this comes up on one of these forums, the anecdotal evidence usually seems to heavily favor DOT5.

 

Just sayin'.

 

Ed

Hi Ed,

DOT 3 is, for want of a better word, the bench mark. The rubber seals are compatible with this grade.

Dot 4 has Borate added - not sure what it does but the seals are less happy with it but generally OK.

 

DOT 5 is a different make up but generally silicone is inert and should not affect the seals

 

Why do virtually all car manufacturers not recommend DOT 5. I imagine ABS (or equivalent) is the problem.

When operating, the ABS can generate air bubbles in the fluid (hence the use of DOT 5.1) that are very slow to disperse.

 

I appreciate that our cars do not have such luxuries but the OEM says - do not use. But what do they know.

 

Modern top grade DOT 4 is very good. It also strips paint just like the old stuff.

 

Roger

[stuart]

We have been here so many times before with this argument there is no point in going over it again.If the manufacturers of your part says dont use X with it and you do then no matter what anyone else says if that part fails or doesnt work as originally designed then your on your own. This applies to everything in life.FWIW there is no BS Standard for silicon.

Stuart.

[boxofbits]

Yes its a convoluted argument with no real conclusion.

 

I do find it hard that though that Moss Europe, being possibly the largest single supplier of Classic Car Components are prepared to endorse DOT 5 on their website. Surely they would be opening themselves up to litigation if incorrectly advising owners to use it.

 

https://www.moss-europe.co.uk/dynolite-silicone-brake-fluid-dot-5-1-litre-ggl862110.html

 

Kevin

Edited September 15, 2018 by boxofbits

[RogerH]

Yes its a convoluted argument with no real conclusion.

 

I do find it hard that though that Moss Europe, being possibly the largest single supplier of Classic Car Components are prepared to endorse DOT 5 on their website. Surely they would be opening themselves up to litigation if incorrectly advising owners to use it.

 

https://www.moss-europe.co.uk/dynolite-silicone-brake-fluid-dot-5-1-litre-ggl862110.html

 

Kevin

as do Automec brake pipes.

 

Roger

[Don H.]

...standard DOT 4 Ethylene Glycol...

 

Glycol based, yes, as a broad chemical class. Not strictly ethylene glycol, however. {Don't put antifreeze concentrate in your braking system!)

[RogerH]

Hi Don,

it gets quite cold here in the winter

 

Wiki gives it as glycol-ether or a polyglycol-ether, or polyethylene glycol- I was over generalising.

 

Roger

[ed_h]

Well, certainly the reason this and a few other perennial topics keep coming up is that we have new folks joining the community all the time. It is a confusing thing, so they ask. Going over it again is not totally wasted effort.

 

The admonition against DOT5 for modern cars is surely due to its incompatibility with ABS systems. It's an air-entrainment issue as Roger says.

 

As for our older cars, my theory is that these master cylinders and such were designed decades ago, probably before DOT5 even existed. At the time, there were a number of non-DOT fluids on the market, and there may have been compatibility issues with rubber components. Thus the design documentation for these parts specified to use only DOT fluid (DOT3 or maybe 4 at the time). Todays replacement parts are direct descendants of the original designs, and have inherited the original design specifications, including the direction to use only DOT3/4.

 

Today, the whole rubber incompatibility thing is a red herring, since the rubber compounds that can be used with brake fluid are spelled out in the DOT standards.

 

Ed

[Don H.]

Hi Don,

it gets quite cold here in the winter ...

 

A new concept of brake lock-up then, eh, Roger?

[DaveN]

+1 for Ed’s comments. Our own high street car spares Mr Halfords withdrew DOT5 silicon fluid due to incompatibllity with ABS systems and further confusion arose when DOT5.1 fluid turned up which reverted back to the glycol mix. Some of the boy racers in their 1 litre Corsa’s and polos were unable to read and understand the details on the bottles because they had big words in!

[KiwiTR6]

Just last evening I flushed all of my brake lines out with methylated spirits and compressed air after having previously stripped and cleaned/rebuilt the front calipers, rear wheel cylinders and master cylinder for the conversion to DOT5 silicon fluid.

 

The superb paint work on my car when I purchased it had been destroyed by DOT4 fuid leaking from a faulty master cylinder, and after having spent considerable time prepping and repainting the area I was not going to allow that to happen again!

 

The fact that I may have a little more pedal travel is not an issue in my mind, but learning just now that it was developed by the US military for long-term storage of their vehicles is a real bonus.

 

DOT5 fluid going in today!

 

Gavin

Edited September 15, 2018 by KiwiTR6