Subject: Re: [Shop-talk] Silicone brake fluid

From: Karl Vacek via Shop-talk <[email-masked]>
Date: Sat, 16 May 2020 10:16:30 -0500

Yes, unfortunately you do.

Every silicone conversion failure I've ever heard of (I even cheated on 
this process once and had a failure of my own) has involved contamination 
with conventional fluid.  Flush all hard lines with lacquer thinner or 
similar, all new rubber and hoses, only lubricate the rubber with silicone 
fluid.

I'd be sure to soak the rubber you've already installed in some sort of 
solvent and even then say a prayer that the DOT 3 didn't get too far into 
the rubber.  Conventional fluid is alcohol based, so alcohol might be there 
way to soak the contaminated rubber, then dry well - like a day or more, 
maybe in warm conditions.

Seems that DOT 3 or 4 gets way into the rubber and eventually reacts once 
it's in silicone fluid.  And then people blame the silicone fluid for 
eating their rubber parts and hoses.

Karl

On May 16, 2020 9:14:23 AM Robert Nogueirao via Shop-talk 
<[email-masked]> 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
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From: Bob Spidell via Shop-talk <[email-masked]>
Date: Sat, 16 May 2020 08:33:27 -0700

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Agree.  Usually, the recommended solvent is denatured alcohol (ethanol 
spiked with chemicals to make it undrinkable--well, you /could /drink 
it, but you wouldn't be a happy camper).  I used it to flush my 
Austin-Healey 3000's system decades ago and silicone has been in ever 
since with no issues (that I could attribute to the DoT 5).

On 5/16/2020 8:16 AM, Karl Vacek via Shop-talk wrote:
> Every silicone conversion failure I've ever heard of (I even cheated 
> on this process once and had a failure of my own) has involved 
> contamination with conventional fluid.  Flush all hard lines with 
> lacquer thinner or similar, all new rubber and hoses, only lubricate 
> the rubber with silicone fluid.
>
> I'd be sure to soak the rubber you've already installed in some sort 
> of solvent and even then say a prayer that the DOT 3 didn't get too 
> far into the rubber.  Conventional fluid is alcohol based, so alcohol 
> might be there way to soak the contaminated rubber, then dry well - 
> like a day or more, maybe in warm conditions.
>
> Seems that DOT 3 or 4 gets way into the rubber and eventually reacts 
> once it's in silicone fluid.  And then people blame the silicone fluid 
> for eating their rubber parts and hoses.
>
> Karl
>
>> 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:
>> 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
>

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    Agree.  Usually, the recommended solvent is denatured alcohol
    (ethanol spiked with chemicals to make it undrinkable--well, you <i>could
    </i>drink it, but you wouldn't be a happy camper).  I used it to
    flush my Austin-Healey 3000's system decades ago and silicone has
    been in ever since with no issues (that I could attribute to the DoT
    5).<br>
    <br>
    <br>
    <div class="moz-cite-prefix">On 5/16/2020 8:16 AM, Karl Vacek via
      Shop-talk wrote:<br>
    </div>
    <blockquote type="cite"
      cite="mid:[email-masked]">Yes,
      unfortunately you do.
      <br>
      <br>
      Every silicone conversion failure I've ever heard of (I even
      cheated on this process once and had a failure of my own) has
      involved contamination with conventional fluid.  Flush all hard
      lines with lacquer thinner or similar, all new rubber and hoses,
      only lubricate the rubber with silicone fluid.
      <br>
      <br>
      I'd be sure to soak the rubber you've already installed in some
      sort of solvent and even then say a prayer that the DOT 3 didn't
      get too far into the rubber.  Conventional fluid is alcohol based,
      so alcohol might be there way to soak the contaminated rubber,
      then dry well - like a day or more, maybe in warm conditions.
      <br>
      <br>
      Seems that DOT 3 or 4 gets way into the rubber and eventually
      reacts once it's in silicone fluid.  And then people blame the
      silicone fluid for eating their rubber parts and hoses.
      <br>
      <br>
      Karl
      <br>
      <br>
      On May 16, 2020 9:14:23 AM Robert Nogueirao via Shop-talk
      <a class="moz-txt-link-rfc2396E" href="mailto:[email-masked]">&lt;[email-masked]&gt;</a> wrote:
      <br>
      <br>
      <blockquote type="cite">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.
        <br>
        Here’s the problem:
        <br>
        In rebuilding the cylinders I coated the bores lightly with red
        brake grease and DOT 3
        <br>
        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?
        <br>
        Thanks for any answers.
        <br>
        <br>
        Bob Nogueira
        <br>
      </blockquote>
      <br>
    </blockquote>
    <br>
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[email-masked]

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From: Eric Russell via Shop-talk <[email-masked]>
Date: Sat, 16 May 2020 11:46:05 -0400

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

[email-masked]

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From: Bob Spidell via Shop-talk <[email-masked]>
Date: Sat, 16 May 2020 09:04:39 -0700

I have heard Dawn Dish Soap--the 'miracle' detergent--will remove 
silicones and allow for painting.  No personal experience, however.

On 5/16/2020 8:46 AM, Eric Russell via Shop-talk wrote:
> I would clean them out. It may not be required but now would be the 
> best & (only?) opportunity.
>
> 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
>

[email-masked]

---

From: John Miller via Shop-talk <[email-masked]>
Date: Sat, 16 May 2020 10:38:39 -0700

> I would clean them out. It may not be required but now would be the best 

Now that they've taken rubber-safe chlorinated brake cleaner off the 
market, you have to buy Lectra-Clean
> higher boiling point than DOT 3. And it'd be totally compatible with DOT 3.

I have a hard time understanding why one would want to use silicone.

There's DOT 4, DOT 5.1 (which is not silicone) and now DOT 4+ which 
combines the temperature ratings of DOT 5.1 with the viscosity of DOT 4.

John.

[email-masked]