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MG Midget and Sprite Technical - Silicone brake fluid

My hydraulics are done (brakes & clutch) and I'm wondering about silicone brake fluid. I have heard mixed reviews. The plus is it doesn't absorb water, so if the car sits a lot you don't have to change it often. The minus I heard is that it has a lower boiling point. Also I heard some racetracks won't allow it. So I'm looking for input.
TCW Tom Westcot

don't like it; just change normal fluid every 2 to 3 years, as is the industry recommendation these days.
David Smith

While Silicone fluid doesn't absorb water, any water in the system collects at the bottom and can migrate to the lowest point, where it rusts.

The water migration issue is also the reason for the higher risk of boiling: Silicone fluid actually has a higher boiling point than DOT4 (500F vs 446F for DOT4) but if the lowest point is your brake callipers, then that slug of water can boil easily. If that water were dispersed evenly throughout the braking system (like it would be if absorbed into DOT4 fluid) then it would be less likely to boil.


Growler

Again - some like some do not.

I do as I run very little at present - have used it for years in both B's and midget with no issues.

Other very big positive - does not act as paint stripper either !!!

If you race/hammer it, well its probably not for you.

R.
richard boobier

From what ive researched...its good, but its alot of work and expense to set up properly

You have to ither replace or wash out thoroughly all the lines, cly and parts with denatured alcohol if you do that then all the rubber parts must be replaced as well, so its a little hard to justify the over haul, when castrol LMA fluid works just as good, but without all the hassle

Prop
Prop and the Blackhole Midget

Been using silicone in my road-going frogeye for the past 23 years. Fill and forget.
SA Wood

As SA used it in my Sprites for years and my daily driver too.
Alan
www.masckent.org
Alan Anstead

Dot 5 is not compatiable with dot 3 & 4, or am I wrong

Prop
Prop and the Blackhole Midget

I used Silicon fluid for years in Mini I had some while back - I moved to it after a rebuild to avoid all those nasty corrosive patches around the bulkhead after leaky top ups.
I hardly touched afterwards except to check level every few months. I only used the car for road use - didn't have any issues with seals either...

Having said that every car since I have std fluid in ...
John Barber

Thanks for the information.
Prop I have everything new. Pipes hoses cylinders etc. That's why I'm trying to decide which way to go.
TCW Tom Westcot

When a braking system is good you will not have to top it up.
And putting an old towel down to protect the paint is not that hard either.
So gone is the corrosive argument.

Leaves just the fit and forget argument.
If you want a fit and forget car buy an MX5/miata!!!

Use dot 4 and do the maintence.
You will find you check all kinds of things and catch things before the have gone wrong while doing the fluids
Onno K

have a look around on the B forums here and Paul Hunt's site mgb-stuff as I think those places are where I saw suggestions against its use

I'm very much against standard brake fluid because of the taking the paint off and changing every 18-24 months (or 36 depending on who you follow plus it could be sooner than 18 months) but it was in when I got the car
Nigel Atkins

I've used it and been very happy. Brakes work and the paint job is not at risk when I repair or bleed the system.
Sheldon's 74

Well... now thats a completely differant colored horse

If you have a completely new brakes system, id be strongly tempted to go with a Dot 5 set up....so yes, it a yes vote is what im casting

Go for it

Prop
Prop and the Blackhole Midget

I'm thinking about using it on the Mini, which also has a brand new system. I wonder how it will interact with the PBR brake grease I've assembled the pistons with? Maybe I'll strip them and reassemble with silicone brake grease.

Growler

What is PBR brake grease? I used the lube that came with the kits on the master cylinders and front calipers. The rear calipers are Wilwood. If this grease issue is important I'd like to know.
TCW Tom Westcot

Just a generic rubber/brake grease made by PBR, it seems to play nicely with regular brake fluid but I wonder how it would interact with silicone fluid. It's probably just fine, but given that there's silicone brake grease avaialable I'd probably err on the side of safety and use that.

Here's the PBR generic grease: http://www.amazon.com/PBR-RG17-Rubber-Grease-17-5gm-Tube/dp/B005DGNOEA

And here's the stuff I'll probably replace it with: http://www.amazon.com/dp/B00B3URP1I


Growler

I've used silicon fluid in my V8 MGB for years. No bother at all. It was a brand new system, including pipework.
Mike Howlett

I read somewhere that the U.S. army specify silicone for their vehicles, but if they get one without it they just top up and fill with dot 5. If that is true I reckon it answers your question better and more authoratively than any opinion here :-)
Graham P

Dot 5 is silicon. It is not compatible with Dot 3, 4 or 5.1.
Mike Howlett

Question for SA Wood, are you saying you've not changed your brake fluid for 23 years?

C L Carter

Mike, yes I know dot 5 is silicone, that was my point!
Graham
Graham P

Graham,
>>If that is true I reckon it answers your question better and more authoratively than any opinion here :-)<<
the problem is the if it's true bit means it's not an authoritative statement as such

here's another side - http://www.mgb-stuff.org.uk/braketext.htm#nosilicone

as I said before I dislike the usual brake fluid and think like many things about cars the technology is so old and only retained because it's cheap and possibly easier to make more profit on
Nigel Atkins

*****I read somewhere that the U.S. army specify silicone for their vehicles, but if they get one without it they just top up and fill with dot 5. If that is true I reckon it answers your question better and more authoratively than any opinion here****

Lets think about this... the USA military spends more then ever other country combined except for china and russia To stick our finger in islams eye

I seriously doulbt there conserned with causing $1000 worth of damage to a brake system in afgan

Prop
Prop and the Blackhole Midget

Prop, I also reckon that they don't want the agro of one of their heavy trucks trundling through a shopping mall in the USA cos the brakes fail :-)
Graham.
Graham P

CL Carter

I replaced master cylinder some 10 years or more ago. That was the last time the fluid was "changed". I had to remove one of the rear cylinders a couple of years ago so bled some fluid off but that's it.

Simon
SA Wood

"Fit & forget" - I know for a fact that one MGB GTV8 I know of had silicone fluid in the brakes without any change or even need for topping up for 17 years. The brakes were still fine - I drove it briefly and the brakes worked perfectly well.
Mike Howlett

I have used Silicone fluid for 20 years and it has paid for itself may times over. On completion of the first rebuild, on exiting the A1 to go to Kimber run a rear line fractured, as i had work hardened a fitting, spraying fluid over the back of the car.
However, fit and forget is not a good philosophy.
On the second rebuild now 20 years on, i found water in the front calipers. A point from a previous post.
I always end up spilling the stuff too.
so it may be a good idea to take the front calipers off and drain them, say, every 5 years.

Mike


M Myers

Ive been using it in my mga for 12 years! I rebuilt the whole system and poured the stuff in! Never had an issue with the hydraulics. I blame the longevity of the hydraulics on the silicon fluid! Imho its worth it!


Steven Devine

I did order the silicone fluid but I haven't got it in the car yet.
TCW Tom Westcot

This thread was discussed between 03/06/2013 and 21/06/2013

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