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MG MGA - Brake fluid

As the forum is a little quiet at present, I thought I would raise that old hot potatoe - silicon v glycol brake fluid?
Its just that I have stumbled over the AP Racing web site that says they do not recommend silicon with their own, or any other braking system.
www.apracing.com/Info.aspx?InfoID=49&ProductID=3717

We all know that silicon is much safer when in contact with the paint work, but if it impacts on to driving safety....?


Graham V

I don't believe any of the claims that DOT5 is any less safe than DOT4. The only real-life differences I've seen is the bleeding process being a bit trickier and the purchase price being higher. On the upside, it doesn't eat paint and MGAs all leak brake fluid onto the paintwork at some point.

I use both types of fluids in my cars (ten of them) and have had no issues with either type. I do choose DOT5 for the MGA because of the paint issue.
Steve Simmons

I know a couple of people who have used silicon in their classics, one for decades, neither have problems.

I would gladly use it if I had totally new clutch or brake hydraulics as you can't mix the two so new seals.

When I helped bleed with silicon it was very straight forward.

Some seem to say it gives a slighhlty different pedal feel but I wouldn't know as I've never had the comparison.

One suggestion is that silicon may have cause water/condensation/hydrowotsit to be in certain areas causing rust.

Brake fluid - and paint - should be things from the ancient past in the 21st century but brake fluid is so cheap - and paint relatively so.

Nigel Atkins

Both types of fluid can cause rust if water is allowed into the system. Silicon is not hygroscopic so the water will pool in a low spot and possibly cause localized rust. DOT4 absorbs the water so it will be spread throughout the entire braking system, causing rust everywhere but possibly to a lesser degree in each area. In a dry climate I have never seen any rust whatsoever using DOT5, even on systems which have not been bled in 20 years or more. DOT5 fluid will last indefinitely if not contaminated, and can be filtered and re-used if desired. DOT4 should be changed every year or two because of the aforementioned hygroscopic properties. In a wet climate you need to bleed either type of fluid regularly to ensure the system remains dry.
Steve Simmons

Here we go again. I have always put weight on this document that appeared in Safety Fast in 1999. I did the conversion from hard copy to electronic for them and they gave me permission to use with due acknowledgements.

http://www.mgaroadster.co.uk/SiliconeFluid_1999_11_p29.htm

Steve
Steve Gyles

Changed from Dot 4 last year. Paintwork the decisive factor. Didn't change seals - bled and filled with alcohol (a bruler) - bled and filled with Dot 5 - test ran and then bled and re-filled with fresh Dot 5. Operation over four months since - normal. I am completely with Steve. Now thinking about the Bs and topping up with this different kind of French alcohol.
Roger
Roger Walker

So have you now stopped using SWMBOs old cooking oil for your brake fluid Steve?

I always thought that was the clever dual purpose option, being able to drain it into a metal container, heat it to 180 degrees C to get rid of any water that has accumulated in it and then, at the same time, also cook your French fries in it! The perfect solution.


Sorry bout that, just trying to add a bit of humour(?) into this thread before it gets too serious! :^)
Colyn Firth

Two weeks before the Christmas break I completely overhauled the brake system. It had never been flushed in 58 years! (I know the history of the car.)
And, as I refuse to be draw into this argument -- I used Penrite Super Dot 4.
brakes function perfectly and I didn't spill any on the paint!
Mission successful!
Barry.
Barry Gannon

I am somewhat disappointed that my tongue-in-cheek provocation has not stirred up some fiercer arguments in the MGA community.
Personally I use Dot 4 and have been fortunate not to have any real problems with damaged paintwork etc.
I have never considered switching to silicon for no reason other than my laziness. I wouldn't want to change all the rubber components over as I never had any real problems with Dot 4.
Graham V

To be serious (for once), I can see the advantages of using Dot 5 Silicone brake fluid in a classic car,
its hydrophobic properties means that it is very long lasting and it has no detrimental effect on paintwork in the event of any leaks or spills.
The only downside I have heard is that it is slightly more compressible than Dot 4 and can give a softer pedal.

My brakes are stock Lockheed F Discs/R Drums with Mintex 1144 linings on both and using Dot 4. (No servo)
They are superb brakes with a rock-solid pedal and feel and I can easily lock up all the wheels if stamp too hard.

So, to be honest, I am reluctant to change anything about them.

The Dot 4 does tend to seep very very slightly past the seals on the master cylinder although this is almost undetectable. I have replaced the master cylinders seals but this appears to have made no difference.
(I renewed all of the Dot 4 fluid at the same time)

So, 10 years on from me buying this car, the paintwork below the master cylinder on the bulkhead has developed a very slight "crinkle-finish".
It will be repainted at some point in the future.

However, I am still a little reluctant to swap to Dot 5 in case I lose some of the excellent feel in the pedal.

Colyn
Colyn Firth

"I am somewhat disappointed that my tongue-in-cheek provocation has not stirred up some fiercer arguments in the MGA community."

What do you think this is, that other forum? ;)

I love this forum, it's generally so much more polite than others.
Steve Simmons

Colyn

Did you read the last paragraph in my link? The extra compressibility of silicon will give you about 0.1mm of extra pedal travel. Not sure your studded clod hoppers will notice that!

Steve
Steve Gyles

"Studded clod-hoppers Steve?!"

Ayup, al av tha no, am a Yorkshire-man an am prard ta all-us ware me pit clogs.
(Yorkshire/English Translation available on request)

Yorkshire pit-clogs do have their advantages in an MGA, in the event of brake fluid loss you can use them as emergency brakes by opening the door and applying firmly to the road. You also get some lovely pyrotechnic effects from the steel segs sparking on the tarmac :^)

The disadvantage of pit clogs is that they are so wide that they apply equal pressure to all three pedals at the same time which tends to restrict the road speed :-)




Colyn Firth

Missed the last paragraph Steve, I must admit that, like a typical non-engineer, I skimmed the article and missed that part.

Maybe I will re-consider swapping to Dot 5 when I get around to re-painting the bulkhead to prevent any further damage to the paint.

My brother who is a retired engineer, would have read and studied each page and then be able to quote it word for word.

I would have thought that fighter pilots would have to be a large part engineer to understand and fly modern fast jets.

Cheers
Colyn


Colyn Firth

Colyn

We fighter pilots had very basic engineering skills and understanding. For instance between the throttles and engine it was sufficient for us to describe it as "..a suitable system of linkages". Oil, Hydraulics, grease and fuel were just referred to as "....bit of a fluid leak there Chief". and so it went on.

Like the boots.

Steve
Steve Gyles

All the engineers I know all ready know everything so certainly don't need to read anything by non-engineers but they might skim-read something from another engineer but mainly to spot the 'mistakes'.

For controversy, a friend lives in North Yorkshire and refers to that as real Yorkshire, and there's a chap in a pub we go in that goes on about West Yorkshire, I'm very tempted to say next time I see him "aren't you the chap from East Lancashire?". :)
Nigel Atkins

Steady on Nigel, we don't all have the good fortune to Live in Yorkshire and speak Yarkshire Yammer - some are obliged to live in Red Rose country.
.... and for my White Rose countryman - you don't need to change seals or go to France for the alcohol - meths is worth considering - the downside of my method of changing was the cost of the second litre of Dot5 - most of which is unused.
Roger Walker

My friend that lives in real Yorkshire would say that Colyn has his address here as East Midlands. :)

I've never understood tribalism - football, cricket, counties, there's good and bad in all, tribalism just encourages bigotry.

The few times I've been to Lancashire I've never seen a TVR, bit like the little Union Jacks flying on French and German white vans always makes me smile (inwardly of course I don't want to upset anyone).
Nigel Atkins

You guys just don't realise how tough it is for us Yorkshire men living up here.

It gets tedious from having to having to put up with-

:- The constant ringing noise in our ears from all
those brass bands.

:- The continuous smell of burning lard from a million
sizzling Yorkshire puddings.

:- And worst of all, the sheer exhaustion from having
to constantly wade knee deep through all those
dropped aytch's :^)

Aye, its grim up-North!

Colyn
Colyn Firth

See you're not that far upt' north. :)

I don't mind the weak northern ales as they're so cheap to what us southuners are used to.

Mind we don't get the locals discount, is that legal? :)
Nigel Atkins

Dot 5 in 2 1949 MGTC’s and 1960 MGA coupe...a hard press on the pedal will make all three cars lockup the brakes.
Gene Gillam

Gene
Thats good stuff! One hard press on the pedal locks up all three cars!

Graham V

Dammit...I knew I should have rewritten that sentence!
Gene Gillam

Of course when I was brought up in the West Ridding of Yorkshire we had Riddings and there were only 3 (North, East and West) so I don’t know where that puts Colyn?

By the way now from no less than the KINGDOM of Fife!

Paul
Paul Dean

North Derbyshire, perhaps?
Dave O'Neill 2

I think this is a bit like the other taboo subject: Brexit - many are not letting the facts get in the way of their opinion!
Dominic Clancy

Dominic - why let the facts spoil a good argument?

But I have always thought it strange for the Department of Transport to utilise such very similar codes of DOT 5 and DOT 5.1 for two very different fluids that should never be confused with each other.
Graham V

This thread was discussed between 28/01/2019 and 01/02/2019

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