art

Everything is new, incl flex lines. Steel lines flushed with alcohol. I'm thinking that the silicone fluid will need less maintainence and cause less problems for a car ('75) that will not be driven every day. I did this 20 yrs ago on a Healey, and it is still good!

Any (good) reasons not to do this, like seal compatibility that anyone has experience with?

Thanks

Bob Rouleau

Silicone fluids are incomaptible with some components. Are you sure you will not cause damage to seals etc. Secondly, silicome fluids are low maintenance but at the price of a soft spongy pedal feel quite different from the brick wall feel of a 911 brake pedal. With SS lines you enhance the firm pedal, with silicone fluid you flush away the benefit.

My $,02

Gary R.

The only bad thing that I know of is that condensation isn't absorbed into the DOT5 brake fluid, as it is with DOT3 or DOT4 brake fluid. This moisure can cause corrosion. The DOT5 fluid does have a higher boiling point which may make it more suitable for racing applications, and it doesn't eat paint. The reason for a flushing DOT3 & 4 every couple years is to get rid of the contaminated fluid (containing moisture in solution). I would assume changing the silicone fluid and flushing the system would get rid of the water, but not sure..

I also could be way off base as this is just what I have read.

pjc

Art,

I've had DOT 5 silicone in my '76 911 for 16 years, never changed it, and its still fine (hasn't gone clear either which is unusual). I take a different view on the 'soft pedal' notion; this can be a problem if the system is not bled thoroughly, it is much more difficult to completely eradicate air when filling with silicone - bleed plenty and then some more - I prefer a vacuum fill rather than pressure fill for that reason.

Sorry Bob but I haven't seen any benefit with SS lines (I assume you mean the flexibles here?) over new OE rubber. My 911 doesn't have servo so would expect to see spongy pedal and difference between SS and rubber if it were there. Have to confess that currently have SS on my car - downside is that if I want to remove the caliper I can't squeeze the flexible off, the other downside is that I can't see what's going on behind the SS so the only solution is to replace after X years automatically, which is probably not a bad thing.

That's my experience for what its worth.

PJC

art

I didn't think of the fact that condensation (if it occurs at all) could end up somewhere else and cause problems, but the only place it could go would be in the plastic reservoir, so maybe no problem there.

The spongy pedal thing is urban myth, I think it only happens at extreme temps if at all. Rubber vs. teflon/braid lines is also urban myth designed to sell stuff. I put them on my 914 years ago and noticed no difference.

Peter Zimmermann

I've never recommended silicone fluid simply because it's one more thing that you have to carry with you everywhere that you go. If you have brake trouble on the road, and don't have extra fluid in your trunk, where are you going to find some? I'm not aware of any advantages that silicone has over today's super fluids, that are compatible with almost everything, so I've never even considered using silicone myself.
Pete

Bob Rouleau

PJC - I agree with you. I use the rubber lines. Some switch to the stainless steel lines (racing type) because they flex less and you get a better, firmer pedal. Trouble is the racing ones need constant inspection which we don't do on street cars.

As to fluid, I like ATE blue/amber for most purposes and Motul 600 Racing for track. All are dot 4.

Peter Zimmermann

And let's not forget, most braided hoses are NOT DOT approved...
Pete

Cloggie

I have had silicone fluid for a long time, it is a bit tougher to bleed as the bubbles apparently are not as mobile as in conventional fluid. I have used gravity bleeding (did it a few times to be perfect). Feel is not "excellent", but it is pretty darned good and is no problem either on the street or track.

In terms of compatibility, there are no issues with any components you will be using in your car. The real issue with silicone fluid was that people flushed their conventional systems with silicone, but there was enough conventional, water absorbing fluid left in the crevices and crannies in the system to still have corrosion....

In a new system, I would completely recommend it, if I break down on the road and can't get silicone, I would just add conventional as required (they will work together) and then change to a conventional fluid and all the changing that entails from that point forward.

A neat benefit is that it does not damage paint or anything, so no issues with spilling. Only real negative is that I seem to go through more brake switches than normal (although it seems everyone has problems with them)....I am on my 3rd set in 8 years.....

Dennis

pjc

Pete,

The main advantage for me is that '76 911 is a garage queen and only used on high days and holidays (we get less great sunny days on this side of the pond unfortunately) and with DOT 5 silicone I can forget about the fluid going off - as I said, it's been in the car for 16 years and apart from the obvious maintenance that requires topping up and bleeding it is untouched.

Doesn't suit all but it suits my circumstances.

PJC

Peter Zimmermann

PJC: And that is all well & good. I just remember back to when my shop had to replace a master cyl. on an SC. The car's reservoir had a neatly printed tag that stated "DO NOT REMOVE - SILICONE!" Of course, our customer wasn't available by phone, we had no source for the fluid, did the replacement and had to push the car, unfinished, off the hoist until we could locate the owner, and his fluid. I do realize that the stuff works, and it certainly sounds like it's the right product for you, so it's an "all win," and that's always good!
Pete

pjc

Pete,

Yes I can see your point - whenever my car goes into the shop (always the same one) it goes with 1/2 litre of the brake fluid and they are told everytime that silicone is in the brake system and where to find the bottle, my reservoir also has the label you mention. For most work I hang around anyway and talk to the mechanic and watch what is going on and learn - the Porsche specialist (not a Porsche Centre) are into the cars and appreciate that (some) owners are too.

They probably think I'm paranoid but at least it saves potential problems - so far so good!

PJC

Peter Zimmermann

PJC: I've got a question for you. What are the storage requirements for silicone fluid? We all know that you don't want to keep an already-opened container of conventional fluid lying around for years... does the same go for silicone?
Pete

pjc

Pete,

Because it does not absorb water (at all) it can be left almost indefinitely in an opened container. If left in the sunlight it will however lose its colour (goes clear). I've had a half litre bottle - half used - for about 10 years and its as good as new; also kept in the dark so has retained its blue colour. What is interesting is that I changed my master cylinder 18 months ago so purchased another half litre; I was asked if the fluid in my car had gone clear and when I said 'no - it was still blue' they were quite surprised.

PJC

911pcars

PJC,
In your application, sounds like DOT 5 Silicone BF is fine.

Sherwood