[Mgs] Moss Motors clutch master cylinder brake fluid

[Paul Hunt]

DOT4 has a higher boiling point than DOT3, DOT5.1 has a higher boiling 
point than DOT4 about the same as DOT5 and LMA.  It's said that there is 
more involved than just flushing when you switch between DOT5 and any of 
the others, it can sludge if any remains and they mix.  DOT5 doesn't 
harm paint like the other three do, but instead of absorbing water it 
absorbs air and can make for a spongy pedal.  The same amount of water 
gets into a DOT5 system as any of the others because the cap is vented 
and draws in what could be moisture-laden air as the system cools down.  
But instead of being absorbed and so removed when you replace the fluid 
in DOT3/4/5.1 systems it can remain in the system and if it gets to the 
calipers can boil.  I remember reading a piece from the American 
military some time ago asking the SAE to investigate replacing DOT5 with 
other fluids without having to replace the complete braking system.

PaulH.

On 30/08/2023 19:08, wkilleffer at epbfi.com wrote:
> For whatever reason, my memory isn't always spot-on, but I'm pretty 
> sure I was using DOT 3 with the previous clutch hydraulics, so that's 
> likely to be what I use moving forward. Once I get it disassembled, 
> I'm going to blow compressed air through the metal line to clear out 
> any old fluid. Never used DOT 5. Understand it has some good qualities 
> along with more than a few drawbacks.
>
> About six months ago, I bled the clutch system til clear fluid ran 
> out. The fluid that came out at first was black. I didn't think I was 
> having that much trouble, so after bleeding, I put it all back 
> together. Now, everything seems to point of it suffering a failure 
> somewhere along the fluid pathway, so changing all the components will 
> at least let me know how old everything is because I'll write it down 
> in the maintenance notebook.
>
> Thank you,
>
> -William
>
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