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MG MGA - Silicone brake fluid naysayers please read this

Hi folks. For a long time, there has been a debate raging about the use of DOT 5 brake fluid, otherwise known as silicone brake fluid. I have been using silicone brake fluid in my MGA 1500 for almost twenty years now. During that time, I have NEVER had to replace a single brake or clutch hydraulic component! Not so much as a rubber seal or rubber brake hose! (until now) Although my brakes are still working fine, my master cylinder has recently started weeping a bit of fluid past the Master cylinder outer dust boots. (More on this later.) For the last several years, I have been answering people's questions about silicone brake fluid. My general comments have been that silicone fluid is fantastic! My reasons for saying this are that silicone fluid actually preserves rubber seals, doesnt absorb moisture, so brake cylinders dont rust or corrode, and it doesnt eat paint like "regular" brake fluid does. I have NEVER had ANY problems whatsoever with using silicone brake fluid, except perhaps that it is a bit more difficult to get all the air bubbles out when bleeding. This evening, I removed and dismantled my long untouched master cylinder. When internal parts were removed, there were numerous microscopic rubber particles in the fluid, indicating that the rubber seals finally gave up the ghost. However, after cleaning and examining the Master cylinder bores, I can happily report that they are completely unworn, and unpitted! The pistons were also unrusted, unpitted and looked almost new! In short this master cylinder's bores and pistons are in pristine condition, so the Master cylinder is very rebuildable. Please also note that I have NEVER flushed my brake or clutch hydraulic system in all the years that I have used silicone brake fluid! Surely the longevity and unworn condition of the internal parts is compelling proof that silicone fluid is an excellent product, and is generally a very good choice for British cars, including our prized MGA's! I am hoping that this ramble will help convince anti silicone fluid folks that this stuff really has some significant advantages over other types of brake fluid. If there are any negatives in regard to using silicone brake fluid, I have not found any. Cheers, Glenn
Glenn

Glen - I can back up your experience with silicone brake fluid. I installed it in our TD when I restored it twenty five years ago. Since then it has never been flushed or replaced and is as crystal clear today as the day I installed it. Like you I had to replace the seals in master cylinder at about twenty years, but beyond that, I have not had to do any maintenance on the TD's brake system. Cheers - Dave
David DuBois

I'm a mere sprog with 9 years use. Same fluid in my car all that time. Great stuff. Never a hint of a problem. Everything was totally new in my braking and clutch circuits when I filled up with silicone fluid, so no chance of cross-contamination.

Steve
Steve Gyles

I switched over to silicone this past winter and couldn't be more pleased.

I didn't even have the master cylinder sleeved. I can report no leakage anywhere in the system.

Tysen
Tysen

I spout the virtues of silicon fluid whenever the subject is brought up. Using it since the 80s will never go back to the old stuff.
R J Brown

Quick question - I am right now renewing my brake lines and have replaced one rear brake cylinder and my clutch slave cylinder. Is it okay to refill with silicone fluid or do I have to replace all the rubber seals?

Roy.
R. Maher

Roy - To avoid any compatability problems, make sure that you flush all of the old fluid out of the systems using something like brakeclean and replace all of the software (rubber components) that have been in contact with the old fluid. Cheers - Dave
David DuBois

Forgot one item, after flushing everything with the brakeclean, blow all the lines out to insure that they are dry before reassembling. Cheers - Dave
David DuBois

Thank's for the heads up David.

Roy.
R. Maher

Glen and all:
I agree totally with Glen's observations. I have used DOT5 in my MGA and BGT since 1985. Never flushed the systems except for re-building the calipers in the A and replacing brake hoses. Internal parts were very clean.
I'd recommend replacing ALL rubber bits and flushing the old fluid out before changing to DOT5.
Cheers! Fraser
Fraser Cooper

All, I'm a first time MGA owner, so please forgive my ignorance. How do you flush the clutch line since it shares the same master cylinder? What components need to be changed (rubber parts) if any in the clutch system? Thanks for your patience.
Steve Jackson

I too agree with everyone.

I've had silicone fluid in my BGT V8 for 10 years. Before moving to silicone I rebuilt the entire system with new components, except the servo, the servo failed last year after 9 years, and I don't believe that silicone fluid was responsible.

I had silicone fluid in my MGA during my entire period of ownership - 6 years - without problems. In this case I simply drained the old fluid, flushed the system, and refilled with silicone. I did not replace the "soft" parts, but they were fairly new at the time.

I always use Aeroquip flexible hoses, which I believe, help in keeping the pedal firm:-

http://www.aeroquip.com/pages/performance.html
Nigel Steward

I'm on 18 years with Si Fluid, and when my seals in the clutch MC failed (they wore out after 100k miles), the cylinders and pistons in all cylinders (I renewed all the braking and clutch rubber components on the car at the same time) were like new.

I know that is not possible with normal brake fluid.
dominic clancy

What is "brakeclean" and where can you get it?
Chris Wright

Brakeclean is an aresol brake cleaner that is available at most auto parts stores. Cheers - Dave
David DuBois

I had a bad experience with GE Silicone BF back in the late 80s and swore off SI. I have since realized that what I put up with was more likely a GE product problem, and not one related to SI fluids. (Notice that they no longer make the stuff!)

Also, I think that much of the info available about its use and the cautions we have seen over the years is OLD info and probably does not reflect your almost universally good experience with it. We sometimes forget that even products like SI fluid are under continuous improvement over time, and what was true yesterday, is no longer true today.

Someday, when I get around to renewing my 68 GT's brake system, I will change from the Valvoline Synthetic BF I have used for years to SI. It too is a good product, but I like your experiences and endorsements of SI fluid better.
Bob Muenchausen

I endorse all that has been said in support of Silicone fluid. My TF (which was sold today!) was restored in 1986 and silicone fluid was used in the braking system. In 2004 there was a slight weep from the master cylinder - on dismantling to replace the seals, it was found to be in as new condition; not a mark ub the cylinder and fluid was clean and clear. To be absolutely certain, I dismantled one wheel cylinder - same condition.
Peter Daley

I too endorse all the positive comments on Dot 5. I have used it since 1978 in my Norton, MG and Sunbeam systems. I have one of the few Sunbeams with a working original brake booster. The only downside to Dot 5 is possible problems with ABS...
Gary Moore

This thread was discussed between 20/06/2006 and 26/06/2006

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