[Shop-talk] Silicone brake fluid

[Eric Russell]

I would clean them out. It may not be required but now would be the best 
& (only?) opportunity.

Alternatively, suggest the use of DOT 4. It is 'regular' brake fluid 
(even though the label on the can will likely say "synthetic") with a 
higher boiling point than DOT 3. And it'd be totally compatible with DOT 3.

DOT 5 (true silicone) has two advantages. 1) it won't eat at paint if 
spilled/leaked and B) it doesn't absorb H2O. However it is more 
expensive and, despite not absorbing water it should still be flushed 
every few years. And if it is spilled/leaked will make repainting 
problematic. (I've heard some painters won't touch a car that has been 
'contaminated' with silicone). Since DOT 4 is not expensive, regular 
flushing every few years is not so dear. And DOT 4 is readily available 
should one need a supply while away from home. May not be true with DOT 5.

Eric Russell
Mebane, NC

On 5/16/2020 10:06 AM, Robert Nogueirao via Shop-talk wrote:
> I’m helping a friend rebuild her brake system. All new lines and hoses. I’ve rebuilt the calipers, brake cylinders and master cylinder and they are ready to install.
> Here’s the problem:
> In rebuilding the cylinders I coated the bores lightly with red brake grease and DOT 3
> Fluid.  Now she tells me she may want to go with Silicone fluid.  Does that mean I need to disassemble and wash out all the cylinders and calipers?
> Thanks for any answers.
>
> Bob Nogueira