Silicon brake fluid

I NEVER use silicone brake fluid.

 

I have had a few British cars and I replaced the fluid on one of the XKE's with silicon. The fluid ate through the master cylinder seals an gummed up the calipers quite badly. I am told the advantage is that it brakes with less give and that the fluid is not hydroscopic (condenses with water). I won't ever use it again. It was an expensive mess!

 

Silicon brake fluid is not approved by the TUV in Germany and for good reason. It is terrible fluid. If the DOT was doing its job it would be banned in this country as well.

champtc said it has less give, I assume you mean compressability. Nothing could be further from the truth. Its compressability is very high and gets worse fast when it gets hot and is the primary reason it is not approved by the TUV.

It may not be hydroscopic but tests have shown that does not prevent water moisture from entering the system. Instead of going into solution as it would with glycol brake fluid it remains seperate. Since water is heavier than brake fluid that means it will settle to the bottom rust the components there and since it is at the bottom, in or very near the calipers you now have brake fluid that boils at 212F or about the temp you can count on getting on a trip to the grocery store.

Silicon brake fluid was a hoax perpetrated by the Dow Corning company.

 

I agree 110%!

The mere fact that does not mix with water is the real problem...and rust will form within the brake system, guaranteed. If one were to start with a 100% new, all virgin components brake system, this may not be a problem initially. But...for any fluid to flow within a hydraulic system, the system must be vented to the atmosphere. And we all know that there water present in air...So, over time, water and rust will be present in your hydraulic system.

I stopped useing silcone brake fluid in customer cars over twenty years ago, as the hype of it's benefits far outweighted the damage we were seeing on many customer cars (who wanted the "latest and greatest" fluids...)

David

 

My experience with silicone brake fluid has been quite good.

I restored my Lotus Elan in 1981, drained the brake system completely, cleaned out all tubes, replaced flexible lines and all seals, and poured in silicone fluid. I used the car until 1994, didn't touch the brake system at all, and had absolutely no problems. When I restored the Elan again, the calipers went out easily and there was no rust (a problem with the first restoration in 1981). I used silicone brake fuild again. I know it's not recommended, but I even went racing with the Elan. I use the Lotus about 300 miles a year, more when I was racing it.

I had silicone brake fluid in my Lotus 23 (10 years), my Lancia Stratos (since 1986!), and a 1948 MG TC (the previous owner used silicone fluid, and I've had the car since 1994). Again, absolutely no problems so far. When I overhaul the Dino's system, I will probably use silicone fluid.

The advantages of silicone to me are: it doesn't strip paint (essential on a fully restored car) and seems to live to clainms of long life.

My conclusions are:

1. Silicone fluid works with most cars and are great for cars that see little use.

2. It is specially useful if one has several cars and can't change fluid annually.

3. One should change all seals and hoses, clean out hard lines (with air and alcohol, in my case) before shifting to silicone.

4. It would be wrong to avoid it like the plague.

Just my experience.

Andy

yit would be wrong to avoid

 

When I got my 1973 Pantera in 1990 the PO had rebuilt the brake system and refilled with silicone fluid.
When I replaced the front calipers shortly after purchase with slightly improved ones, I refilled with silicone.

I have not flushed the system since and have had no problems.
A disadvantage is that the pedal is soft-- yes, silicone is compressible and it's impossible to get all the bubbles out.

The argument that it will absorb water from the air like DOT 4 fluid does is not valid, it seems to me-- silicone and water are not miscible.
The only way you could logically rust thru a line would be if you had old DOT 4 fluid in the system which had absorbed water, then flushed silicone fluid thru. This could trap some of the old, wet fluid somewhere in a hard line and it could rust thru eventually. If what had been in the hard lines was fresh, anhydrous fluid, this could not happen.

Personally I would change back to DOT 4 fluid just to get a firmer pedal if doing so did not require rebuilding the entire system, but it is not worth it to me.

Some years ago I saw an excellent article in Road and Track, as I recall, that described the details of exactly which seal types were compatible with silicone fluid and which were not. But the main lesson was that you should never MIX silicone and DOT 4 fluids in the same system because they interact in such a way as to virtually guarantee seal failure.

 

When I finished the restoration of my car (1930's British car) I seriously considered putting in silicon brake fluid for the sole reason that it does not eat paint. The brake system was brand new anyway and I thought it was a good time to do it.

Several people in the club recommended against it and I chose not to. It really is not a big deal to bleed the system periodically AND it gives you a good chance the check out the other parts like the suspension. I have driven cars with silicon and the pedal feel is different, I did not like but I also fully expect that after a few hundred miles the pedal would feel completely normal.

The "does not eat paint" is really the only reason to use silicon fluid, the water thing is not a good reason since proper maintenance should still be done.