Can I use silicone break fluid?

Hello, I would like, if possible, to use Silicone break fluid in my 1983 Daimler Sovereign. Does anyone know if Silicone fluid can be used safely in these cars? I know there are some manufacturers cars that it can't be used in (Rolls Royce, Citroen?) because it rots the Silicone seals in the breaking system. Any input would be much appreciated. Thanks, Andy

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273
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You could use silicone brake fluid, but you may not be happy with it. It tends to give the brakes a spongey feel due to trapped air and that air is difficult to get out.

I don't know of any silicone seals in the brake system. Most of the manufacturers use neoprene or rubber.

Check factory service bulletins concerning DOT 5 spec brake fluid.

I used it in my "E" for many years.

Richard H. Kuschel "I canna change the law of physics."-----Scotty

Reply to
Richard Kuschel

I tried using it for a while but (like you) found that it was difficult to bleed properly. I had a bubble in the clutch line that refused to budge. Silicone fluid is so much thinner that regular stuff that it will flow around many bubbles rather than move them to the outlet. The only real advantage to silicone is that it will NOT absorb moisture over time, negating corrosion and possible boiling of fluid under extreme breaking. Simply changing fluid once a year will avoid this problem. It's also a good way to flush out any crap (it's amazing the kind of stuff that builds up in a closed system). If silicone gets on the paintwork it's damned near impossible to get it properly clean. I've a spot behind the front wheel where a leak contaminated the primer. I had to strip the primer over a large area to get the primer and paint to stick again. I went back to the regular stuff and haven't looked back. Like sex, silicone brake fluid is overrated. PS: finally got my Jaguar website up:

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Reply to
throwaway8

At least that's surely better than having ordinary brake fluid remove the paint.

Ideally silicone should be used in a completely new brake set-up. It definitely does not like be mixed with even a small amount of ordinary brake fluid. I have read that flushing the system with metholated spirits will clean the system but I don't know how successful it is. All I know is that -

  1. On my MGB years ago I drained the standard fluid and as the silicone didn't like the traces which were left behind it ended up costing me a brake servo, and I went back to standard brake fluid.
  2. When I rebuilt my 1953 MG YB with a completly new brake system I filled with silicone liquid. I experience no spongyness, the braking is good and I haven't needed to do anything over the past 20+ years.

( My Daimler still has standard fluid as I've only had it a few months and have had other concerns with that to occupy me.)

Peter C.

Reply to
cornelp

Thanks all, I'm putting my master cylinder back together in the next couple of days, so I suppose it's decision time... Andy

Reply to
273

As a follow up to this, I rebuilt my master cylinder with a repair kit and, during the second attempt to bleed the system (you're not kidding about silicone being hard to bleed...) found that my master cylinder is still leaking (pedal travels to the floor sllooowly, when pressed firmly). Is the silicone fluid likely to have shown up the flaws in the master cylinder, or caused problems with the seals on installation. I'm concerned as the car has only got 32K on the clock (MOTs etc. point to it being genuine), and the master cylinder appears to be shot...

Reply to
273

Reply to
cornelp

I've also had the experience of replacement seals not being up to par. Because our cars are so old and parts inventory so slow moving, stuff can sit on shelves for decades. You may indeed have bad seals. The silicone fluid will exaggerate faults, but it'll leak no matter what is used if the bore is sufficiently worn (or corroded). Bob.

Reply to
throwaway8

Thanks for that input, I must admit that had crossed my mind too. Jury's still out, I may take the master cylinder to someone more experienced to check for signs of corrosion etc. Just to be on the safe side. I am beginning to wish that I'd taken the car somewhere to have the seals done, bleeding brakes are (I mean is) a pain! Inboard brakes were such a great idea...

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Reply to
273

A master cylinder may well not function correctly with anything but

100% sealing and any possible wear not bad enough to be obvious to the eye. Conversely my Daimler rear brake cylinders (outboard brakes!) are obviously 'not smooth' but nevertheless seal quite adequately. Are you sure that your 'gentle to the floor' is not due to compression of the mix of silicone and ordinary hydraulic liquid! I did emphasise that the two do not like each other; even in small quanities. If you didn't flush out ALL the ordinary liquid before inserting the silicone try flushing again with meths before replacing with a fresh lot of silicone. (A mixture is apparent by becoming a white'ish 'foam'; which is probably full of air and will therefor not give a suitably 'hard pedal' on depression.
Reply to
cornelp

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