Silicon Brake fluid
- Thread starter V8P6B
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ripvanwinkle
New Member
I recently rebuilt my NADA P6B brakes from the ground up , including a ridiculously expensive new OEM master cylinder and air valve . The new cylinder's paper work specifically forbade the use of silicone brake fluid . There was no explanation , just a simple very clear statement !!
Cheers
RVW
Cheers
RVW
I have attached a link to an article on Silicone Dot 5 brake fluid.
When I rebuilt my brakes only in the last few years, I recall looking at a bottle of this brake fluid, and although I cannot recall the fine details, I do remember that the disadvantages far exceeded any benefit if any.
http://www.britcycle.com/Manuals/DOT5.htm
Ron.
When I rebuilt my brakes only in the last few years, I recall looking at a bottle of this brake fluid, and although I cannot recall the fine details, I do remember that the disadvantages far exceeded any benefit if any.
http://www.britcycle.com/Manuals/DOT5.htm
Ron.
The Rovering Member
Well-Known Member
The thing that's always instantly put me off the idea of using silicon fluid is that it's supposed to give the brake operation a spongy feel. I simply could not live with that. Anything other than a lovely firm action (Oooeer Missus!) & I'm nervous.
keynsham1
Active Member
I have used silicon brake fluid, and know plenty of other people who have, for many years. I know no-one who has had any problems with it at all. I have read that it has slightly less lubricative properties, but I don't know what that really means. If it is 1% worse for example, and 50% worse would still be OK, then it makes no difference. We have no real data other than hearsay and peoples personal opinions to work with, and I have found this source of information usually to be wrong! Do you think you could legally use it on the road if, for example, there were lots of cases of it jamming servo's and brakes not coming off? I suspect not. It is commonly used in the USA, and if it is good for their safety and testing requirements, who am I to argue!
Tor
Well-Known Member
My 3500S has had silicone in it for the past two decades most likely, has little red advisory labels on the reservoirs about it. I'm about to refurb the rear calipers and unsure what to do as the fluid is old and should be renewed. The dual circuit system seems to make the pedal action a little spongier already, and if regular fluid will make it firmer I'm of a mind to make the change. Keen to hear from anyone who's tried both.
P6 owners locally uniformly hate silicone, they say it eats the reservoir cap seals and allows more corrosion than normal fluid. Seems there are two camps on the issue. It can get a little confusing! This car has lived in a tempered garage, seeing very few road kms since the turn of the century. Still there's only a weepy rear caliper that needs attention.
P6 owners locally uniformly hate silicone, they say it eats the reservoir cap seals and allows more corrosion than normal fluid. Seems there are two camps on the issue. It can get a little confusing! This car has lived in a tempered garage, seeing very few road kms since the turn of the century. Still there's only a weepy rear caliper that needs attention.
keynsham1
Active Member
I suspect that spongy brakes after a long period of time could be flexible hoses expanding, and not necessarily the fluid. It could be either. It could be that as silicon brake fluid doesn't absorb moisture, then any water in the system is free and more likely to cause corrosion?
I am doing that guessing thing again!
I am doing that guessing thing again!
I think the issue is with the silicone fluid not being compatible with certain rubber seals, making them eventually swell up or degrade, with potential failure. That is my understanding of it, and if the normal stuff was good enough then, so it should be good enough now in my opinion.
Simon
Simon
Tor
Well-Known Member
Well I've had the rear calipers out for the classic seals job. On inspection there is a little corrosion on the main piston where it's been exposed to the elements but not within, ie. the part that was inside the bore. The bore feels smooth but looks 'discoloured' in places, as with the hydraulic piston/bore. The LH caliper housing had half-congealed wads of silicone and crud inside in quantities, and wherever this had coated the inside of the cap corrosion or tarnishing of that copper-like surface was non-existant. Maybe thanks to the silicone's anti-corrosive properties?
Only thing is, I haven't had brake grease to lube the internals and handbrake lever with. How crucial is this guys, is it a temperature issue? I also put some copper grease around the outer part of the main piston.
Reassembly is pending a spare nut (the one with two o-rings on it) for the pivot assembly, which was missing when I took the calipers off the car - one was loose but held in place thanks to the spring-loaded nut covering the allen bolt, the other one was just not tight...
Only thing is, I haven't had brake grease to lube the internals and handbrake lever with. How crucial is this guys, is it a temperature issue? I also put some copper grease around the outer part of the main piston.
Reassembly is pending a spare nut (the one with two o-rings on it) for the pivot assembly, which was missing when I took the calipers off the car - one was loose but held in place thanks to the spring-loaded nut covering the allen bolt, the other one was just not tight...
Tor wrote,..
Hello Tor,
I generally use a water resistant high melting point grease for lubricating the ratchet mechanism and the handbrake linkage. For the piston cup I prefer to use rubber grease given that it remains in contact with the surrounding rubber 'O' ring.
Ron.
Hello Tor,
I generally use a water resistant high melting point grease for lubricating the ratchet mechanism and the handbrake linkage. For the piston cup I prefer to use rubber grease given that it remains in contact with the surrounding rubber 'O' ring.
Ron.