British "rubber" used on wheel cylinders and master cylinders apparently has a
higher content of "true" rubber than American or most other import
manufacturers. DOT3 Fluid supposedly will cause this rubber to deteriorate
after
some period of time.
Both Castrol LMA and "Silicone" fluids eliminate this and and also avoid
moisture
mixing in with the fluid. However, "silicone" fluid has a tendency to cause
sponginess in the pedal. The best all around bet is LMA from Castrol.
I'm currently in the process of restoring a '59 Land Rover, and spent lots of
time trying to get the "sponginess" out of the brakes after rebuilding them.
The
LR drum brakes are hooked up quite differently with the springs, etc. than an MG
or most other convential drum brakes, and I thought I had done something wrong.
After lots of phone calls to the LR experts out there, and then MG friends it
became apparent it was probably the "silicone" fluid I used. So, I switched to
LMA -- went through 3 quarts -- making sure I flushed out all the silicone, and
finally got brakes I felt comfortable with.
Didn't really know about this problem with DOT3 until now. Planning to redo
both
MG's with LMA in the next couple of weeks.
Bob Wiseman
=> MGB Roadster 1969 Chrome Bumper
=> MGB Roadster 1980 Rubber Bumper
=> Land Rover 1965 Series IIA
=> Land Rover 1959 Series II
Max Heim wrote:
> Thanks for the info on silicone fluid issues. I was unaware of this
> swelling problem. I was speaking of the
> rubber-dissolving-into-goop-and-losing-brake-pressure-or-weeping-fluid
> problem. I deal with that by using Castrol LMA. I have never considered
> using silicone fluid myself, so I withdraw any implied endorsement.
>
> Dodd, Kelvin had this to say:
>
> >Not everything works with everything else. Is about the only true statement
> >on the Silicone brake fluid issue.
> >
> >This is all undocumented spouting, so take it for what it is worth.
> >
> >1. All silicone fluids are not the same. Rubber swelling ingredients have
> >been added that have had good results and bad results depending on the type
> >of master cylinder. There is no way of knowing when and what were added to
> >different brands at different times. This means that as usual, sweeping
> >generalities indicate lack of specialized knowledge.
> >
> >2. In some applications, the swelling of rubber seals encountered with some
> >types of silicone brake fluid can cause brake master cylinder problems.
> >
> >3. It is well nigh impossible to completely clean out a used brake system.
> >Any contaminants (such as water) in the system can congeal into gelatinous
> >corrosive globs that can destroy a brake master cylinder.
> >
> >4. Silicone brake fluid seems to hold up really well to long term storage.
> >Much better than regular brake fluid.
> >
> >5. Silicone brake fluid holds up so well to storage, that one can forget
> >that the system was converted and top up with regular fluid.
> >
> >6. Topping up a system with regular fluid immediately lets you know if the
> >two types are really compatible. Usually they are not.
> >
> >7. Following long term storage, silicone brake fluid makes an excellent
> >brake pad lubricant.
> >
> >
> >Kelvin.
> >
>
> --
>
> Max Heim
> '66 MGB GHN3L76149
> If you're near Mountain View, CA,
> it's the red one with the silver bootlid.
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