[Spridgets] Bad braking

[Bud Osbourne]

If there were "lumps of goo in the various cylinders", it has nothing to do
with silicone and glycol brake fluids "mixing".  The two are incompatible
and WILL NOT MIX/COMBINE.  Period.
Put some of each in a beaker/clear glass container, put the lid on and shake
them up.  Then watch how quickly they separate.

Not sure what "real racers" are using in their brake systems, these days.
But, thirty years ago, when I was a "real racer" (SCCA E-prod. MGB),
silicone was pretty widely used in racing brake systems.  No problem with a
"spongy" pedal, ever........provided that the air was fully bled out of the
system.   I understand that silicone fluid tends to retain air bubbles
longer than glycol-based fluid.  It's all in how you handle the stuff, I
suppose.

My "street" cars have used and continue to use both types of fluid, for
various reasons/personal whims.  Not, I don't put silicone and glycol fluids
in the same system.  Different moisture retention characteristics (silicone
doesn't, glycol does), different boiling points and probably a few other
reasons I'm missing.

Bud

-----Original Message-----
From: spridgets-bounces at autox.team.net
[mailto:spridgets-bounces at autox.team.net] On Behalf Of Mark Haynes
Sent: Monday, January 20, 2014 10:26 AM
To: spridgets at autox.team.net
Subject: Re: [Spridgets] Bad braking

Rick-He said DOT 3 and DOT 4 -NOT DOT 5, which is silicone. Castrol GT-LMA
has ALWAYS been synthetic, but NEVER Silicone. The DOT 3 CAN cause
deterioration of natural rubber seals, that is why we all like the GT-LMA,
since its been used forever with natural rubber seals and has a lower
propensity to absorb water (thus the LMA-Low Moisture Absorbance) than other
brake fluids of the era.
Brian, you don't have to rebuild the whole system, but keep an eye on the
color of the brake fluid, if it starts to darken, then the DOT 3 has started
eating the rubber seals and THEN you need to rebuild the whole thing. I'd
flush the system, after I replace the hoses with new ones, with new GT-LMA.

Mark Haynes
It only goes one way-Pay it Forward


Subject: Re: [Spridgets] Bad braking
Message-ID: <D9F1ED86-13A3-4C0C-BA77-E640B0AD9168 at chartermi.net>
Content-Type: text/plain; charset="us-ascii"

Yikes!  Mixing glycol based brake fluid with silicone based fluid is a
definite bad thing.  I've heard it can cause lumps of goo in the various
cylinders.  This could even be the cause of your brake issues.  Most likely
it's bad hoses though.  A thorough flushing is in order.

And real racers don't use silicone brake fluid as it gives you a somewhat
spongy pedal under hard use.  Silicone "sponginess" is a good thing for
certain applications, but not brakes.  :-)

Sent from my keyboard

On Jan 18, 2014, at 10:20 AM, Brian Morse <owensdad74 at gmail.com> wrote:

> Thank you all for the great info!
>
> I had no idea the hoses would fail in that manner- very interesting.  
> I
will
give Peter C a shout on Monday.
>
> And I will try my hand at searching the archives.
>
> After double checking the fluid I put in I see I used Valvoline dot 3 
> and 4
SYNTHETIC fluid.  I never saw that (duh).  Do I really need to tear it apart
and rebuild the whole system?!?
>
> Bri