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MG MGA - Reducing water absorption in brake fluid

The absorption of water by LMA brake fluid has always been a topic of discussion. It reduces the boiling point of the brake fluid and may cause corrosion of brake parts.
The normal solution is to change the fluid every two years. Some modern cars have a bellows fitted to the inside of the cap of the master cylinder reservoir. This allows the level of the fluid to rise and fall on every use of the brakes without new moist air coming into contact with the fluid. The air is always only in the bellows.
Could this be done on a MGA?
I have put an idea on the Web. Too long for a posting.
Would it work?

http://www.angelfire.com/amiga/mga/Bellows.pdf

Mick
Mick Anderson

Sounds like a good solution but is everyone completely against Silicon fluid for the various published reasons? I've used it for many years with complete success in fact I have a B which has has the same fluid in it since 1996 without a problem. Yes bleeding has to be performed a little more carefully because of the fluids tendency to aerate more easily when bleeding but my pedal is just as hard as it would be with a mineral fluid.
Iain MacKintosh

Ingenious Mick. But like Iain I am a silicon fan since 1997 so will not be incorporating the modification.

Steve
Steve Gyles

Iain,

I am not totally against silicone. I prefer LMA because of seal swelling problems, but I am prepared to admit that this was probably because traces of LMA were still present at the change to silicone.
The evidence and comments received seem to point to this incompatibilty of the two fluids being the main problem.
However, it is a major task to make a change and I am only suggesting options for those who find it easier to stay with LMA.

Mick
Mick Anderson

I'm not sure how much that will help. Glycol brake fluid -- LMA included -- is hygroscopic enough to pull atmospheric moisture into the system straight through the rubber in the the brake hoses. Stainless hoses with telfon linings will help slow this down....
Rob Edwards

Rob,

It is the first time I have heard that moisture can actually pass through the rubber of the brake hoses.
Can you point me in the direction of some chemical engineering documentation?

Mick
Mick Anderson

I'm not a chemical engineer so I don't have ready access to that literature. However, there is plenty of other documentation available on the web, albeit much of it from secondary sources. I once ran across a nice web page wherein the author had taken new, dry brake fluid, sealed into a standard brake hose, submersed it in water for a period of time, and then measured the moisture content of the fluid. He did the same with silicone fluid. The glycol fluid showed significant moisture contamination whilst the silicone fluid showed none. Of course I can't find that page now... :-(

If you'd like to do some research on the subject, there are lots of references out there. Here's a start:
http://www.google.com/search?q=absorb+water+through+rubber+hose+%22brake+fluid%22&ie=UTF-8&oe=UTF-8


I think the bottom line is: flush your brakes! :-)

HTH!
Rob Edwards

Some years ago I was in France in my midget and had cause to buy brake fluid. I was running dot 4 and bought some in a local store. Unlike the UK it was in a metal tin and after using what I needed I fixed the top and placed it in the boot of my car and forgot about it. Sometime later perhaps a year or 2 I noticed a bit of paint stripping near the rear of my car. Over that time period the bottom had rusted out of the tin and the contents had seeped into my boot. If that is what it can do to a sealed tin you need not ask what it does to your calipers and cylinders.
Bob (robert)

Ian - I have you beat, I've had silicon fluid in our TD toe twenty years without ever being changed. It is as crystal clear to day as it was when it was first put in (I have to stick my finger into the master cylinder to determine the depth of the fluid because it can't be seen easily). I guess the bottom line is, no moisture, no crrosion.

Mick - I don't know when you tried silicon fluid, but some of the earlier ones that hit the market did have a problem with swelling. I was probably lucky to have gotten a brand that got it right the first time.
Cheers - Dave
David DuBois

Mick...don't bother with the patent...it's been done. I've worked on few cars with them integrated into the m/c covers.
Jon Bachelor

Rob-This is probably the article about brake fluid that you read. It was written by Nelson Riedel, a retired engineer and professor, and appreared on the Buckeye Triumph website. http://web.archive.org/web/20031212081243/www.buckeyetriumphs.org/technical/Brakes/Fluid/Fluid.htm
Berry Price
BTP Price

This thread was discussed between 28/01/2005 and 30/01/2005

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This thread is from the archive. The Live MG MGA BBS is active now.