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MG MGA - MGA Master Cylinder

So once again Spring is here and my 3rd rebuilt master cylinder from white post has leaked silicon fluid all over. At 250.00 a pop I might add. Of course the warranty is voided because I used silicon brake fluid.

Those of you who say I deserve what I get for using silicon fluid....lets just head you off at the pass.

My car has a very nice paint finish...there's no way I will consider any fluid that's going to damage it even if I have to replace the master every year.

My problem seems to develop while the car is in storage
not being used. I'm thinking it temperature related.

Once winter subsides and the warmer spring weather thaws us out my master purges its self all over the floor. Anyone have a Solution? I could just refill and it would be fine the rest of the year as it has in the past, but really no one makes rubber parts compatible for silicon in this day and age for these cars?

No need to reply with academic fluid algorithms here.

Just looking for a real usable fix that doesn't require putting a modern master in.

Thanks for your replies in advance!
Steven Devine

You could always try Cuban brake fluid!

http://www.safebraking.com/diy-cuban-brake-fluid-homebrew/
D O'Neill

The statement that no-one makes rubber parts compatible with silicon fluid is (sorry to say) plain nonsense - if it were true then there would not be thousands of people like me using the stuff without problems in their brake systems for years without any problems at all.

The real problem is the oft reported inferior quality of White Post refurbs.

The alternatives are either put up with it or install a Caparo unit - which is optically indistinguishable from the original Lockheed cylinders and is a quality part that will not dump your fluid because of uneven coefficients of expansion in a freezing cold garage.

I have never understood why anyone would refurbish a critical safety part of their car instead of purchasing a new item that costs the same and is guaranteed properly.
dominic clancy

I agree, thre is nothing wrong with silicon fluid. I use it in my MGA for the same reason as you, with no issues. I had my MC re-sleeved locally and then installed Moss rebuild kits. The rubber found in the kits when I bought them (from all suppliers, not just Moss) was a bit off spec and so the cylinder was tight. I honed the sleeves a bit and drove the car, and eventually it loosened up. But never any leaks. It sounds like there is something else wrong. Make sure it isn't leaking between the body and sleeve. That would indicate a bad machining job.
Steve S

I have used silicone fluid in various vehicles over the years with no problem....
Your problem is buying rebuilt m/c's...It is practical to rebuild the slave, but very few rebuilt m/c's work well..
Get a new unit and have fun.
Edward
E B Wesson

One thing I have have started to do when storing the cars for the winter is to back off the brake adjustment all the way. (hard to do with disc) Then I will pump up the brakes with the pedal. My thinking is to work the cylinders over a longer distance to help dislodge any particles and to lubricate the bores, and bed the seals. I really don't know if any of this works... but no leaks.
C.R. Tyrell

I think the worst thing you can do with old British cars, is not use them....In the Winter, I still go out to the garage, start the cars, step on the brakes and clutch, shift gears (in situ), maybe back up a few feet, then forward....Do this once a week, in addition to a battery tender, and you'll be ready for Spring. At least , that has been my experience.
Edward
E B Wesson

Agreed 100%. The best running and most reliable cars I've ever owned are the ones I drive constantly. You can feel the difference when a car has been stored. It takes many miles (and sometimes physical repair) to fully recover and run at its best.
Steve S

Slaves are so cheap I can't see the point of trying a recon job on those either.

It's pointless trying to skimp on hydraulics unless the part is NLA and a refurb is the only way to get a serviceable part.
dominic clancy

Can I jump in here, as I was looking at running silicon fluid too, as virtually all the brake system will be brand new.

But I've just taken the front calipers of the shelf (where they have sat for a number of years) and on opening the box I'm confronted with a sticker saying "do not use silicon fluid, as warranty will be void".

Now not sure what to do.

Chris.
Chris Bond

Ignore it, at worst you have to replace a pair of seals that would in any case be suspect quality if the rubber reacts to silicone. Mine have always had silicon fluid in them and are still fine after 26 years. It is only because they are now so old that I have a set on backorder to replace when they finally produce some again.
dominic clancy

Chris

You say your system is virtually brand new. It is vital that all your system is completely free of the other fluid. This should be done by flushing through with something like acetone.

Ordinay brake fluid absorbs about 12% by volume of water. Any of this stuff left behind can cause problems in the years to come as it is immiscible with silicon fluid and could sit in pockets, causing corrosion and other issues.

It is likely that failure to flush through has been one of the causes of the bad but false name given to the fluid.

Steve
Steve Gyles

To add to what Steve says with any water sitting in pockets it could freeze, perhaps even pop seals out?

Paul
Paul Dean

It would have to be a lot of water.
Steve S

Hi Steve,

The only element that is not brand new is the master cylinder, which I will strip, clean and check. Everything else is new and never seen any fluid. I take it you are running silicon?

Dominic.
Here what you are saying, so I guess I'm in for new seals in the calipers for peace of mind.

BTW.
The calipers are MGB V8 to match the engine!
Chris Bond

Chris

Yes, I have only ever run silicone in my MGA. Whilst I have had the occasional brake issue in the last 16 years, none have been attributable to the fluid - all MC problems. Replacement with Caparo sorted those out, although I recently found the doughnut-shaped seal in the braking side was not seated.

Steve
Steve Gyles

I put silicone fluid in my 1600 MGA about eight years ago. I changed all the rubber parts (hoses and seals) and fitted a new master cylinder. I just used the silicone fluid to flush out the pipes. A few years later someone (with silicone fluid) said that they noticed some contamination when bleeding their car. So I bled a good 100ml or so through each corner. It was absolutely as clean as when it went in. While I cannot recommend not flushing out the brake lines, I have had no problems with this car or indeed with an MGB I did the same with 20 years ago (my brother only had that for another few years though).

The MGA I rebuilt a couple of years ago had new everything on the brakes, and has been running perfectly since on silicone fluid.

Last year, a friend with a totally rebuilt Morris Minor had a new rear cylinder leak after a couple of months (with DoT 4 fluid). Obviously a crap cylinder, but I am sure that if the car had had silicone, it would have got the blame!
N McG

This thread was discussed between 31/05/2014 and 03/06/2014

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