Brake fluid

[bevan]

This is my first post on the forum, have been feeling the urge to join in for some time now and this post has been the trigger.
Some of our learned friends have given you a categoric NO to silicon brake fluid without saying why ?
I have used it in my Ace where it has been sitting quite happily for 4 or 5 years now and with minimal use !
Also some 21 years ago I carried out a total overhaul of the braking system on my sisters Fulvia HF, seized callipers and master cylinder from lack of use.
Needless to say I re filled it with silicon fluid which remains in it to this day and brakes are fine. I think it should be a consideration especially with a brand new system. Automec sell a Silicon Dot 5 fluid which they say never needs to be changed. I can only speak as I find.

[Paul Blore]

Welcome Byron.

I used silicon in my previous Cobra from new and no matter what I did, I couldn't completely get rid of a spongy brake pedal.

Roger, over to you.

Paul

[David Large]

I had silicon brake fluid in my BRA for about 20 years with no problems at all; in fact I don't think I ever changed it. I did change it to a DOT 4 fluid about 7 or 8 years ago because of comments on this site.

David

[morgy]

Thanks for your post Bevan!

I can only go off internet searches regarding silicone use, The only real negative seems to be a 'spongy' Pedal? I guess using silicone in a system that has or had normal fluid in will open up a can of worms but in a completely new system?

SO what are the real life issues with Silicone fluid?

[Roger King]

I used to use Automec's silicone brake fluid in my Healeys, non-servoed, systems. I made this choice purely to protect the paintwork. The pedal was never great, but on three separate occasions in two different cars I had worrying brake issues. The one that scared me most was on a MSA Two-Day Classic, driving carefully down the return route for the Porlock Hillclimb in Devon. This was public road, in with normal traffic so no great speeds were reached. Near the bottom my pedal suddenly went right to the floor and I had virtually no brakes. I was doing about 35-40 and was at a point where i had to choose - dry stone wall, or Merc 300SL Gullwing in front of me... Luckily frantic pumping of the pedal and killing the motor in gear whilst yanking on the handbrake pulled me up, just in time. Checked the levels, fine - I don't know if it boiled, or what - but over the next two years I had similar issues twice more including one in a different car. That was enough!
My other concern is that silicone fluid is non-hygroscopic so absorbs no water. I've dismantled the braking system on 4 cars now that have used this fluid, and in each one I have found that condensation has formed a water layer 'on top' of the brake fluid which has resulted in a significant rust level in the cylinders/pistons etc.
I just prefer to rebleed regularly and check that everything is working as it should rather than relying on the MOT tester's rollers, but it's all personal choice.
Oh - forgot to say - Hi Byron!! and welcome!!

[Paul Blore]

Roger's experience with his brakes has just reminded me that I had a similar experience with the clutch on my previous Cobra on a couple of occasions. The pedal inexplicably went right to the floor with almost no resistance and then after a few pumps, came back to normal. I also had silicon fluid in the clutch system.

The "pooling" of condensation is also a point for consideration. I suspect that having silicon fluid makes owners more inclined to leave it for extended periods, so by the time a problem manifests itself, it's probably more serious that it would otherwise be.

Paul

[bevan]

Hello morgy

It looks like it would be a brave man who uses silicon brake fluid in the face of comments received. I confess I used it in all innocence after seeing first hand what happens to a neglected system using conventional fluid. None of my other cars have it in them.
Roger is right about lack of use being the enemy and his advice is sound about changing every few years.

Meanwhile I will continue with the silicon in my Ace and see what happens ! May be be a bit more circumspect when driving it after the IVA.

[Roger King]

Hi Byron,

The fact is that there are no right or wrong answers. We make our own decisions based on experience, and maybe advice - the truth is that any braking system needs regular monitoring and maintenance, there are no easy shortcuts!

Happy Christmas!