[DML] why DOT 5? (was: Brake fluid)

["Farrar Hudkins" <fhudkins@xxxxxxxxx>]

Bob,

If I may be forgiven for veering off topic to satisfy my curiosity: Is
there any particular reason you are using DOT 5?

>From what I've read, DOT 5 has a higher boiling point (500F) than DOT
4 (446F) or DOT 3 (401F) -- but because it is silicone, it will not
absorb water, and a globule of water can sink to the bottom of the
system, boiling at 212F and causing brake failure. DOT 4 would seem to
be fine for most automotive purposes, but I don't know how you've
upgraded your braking system.

Somebody feel free to tell me if I'm wrong (like I need to say that on
this list... LOL): my understanding is that because DOT 4 is
glycol-based it can absorb water -- the advantage being that your
brakes will work when water is present, and the disadvantage being
that they won't work as well. (However, when you notice them not doing
as well, you can drain the DOT 4 and water, fix the leak, and put
fresh DOT 4 in.) The difference in boiling point of silicone-based DOT
5 versus glycol-based DOT 4 is negligible, in my opinion, because I
drive my DeLorean pretty casually.

I haven't followed the progress on your car very closely -- sorry. Is
there a blog on it? Or if you have the time to explain, I'd like to
know more about how you have upgraded the braking system -- and how
hard you plan on driving it ;-) -- if you've necessitated the use of
DOT 5 fluid. This cat is curious. :-)

Farrar Hudkins
#2613 (auto -- waiting on parts)

On 4/18/08, Bob Brandys <BobB@xxxxxxxxxxxxxx> wrote:
>
> After recently replacing the leaking master cylinder on the 2015 De
> Lorean,
> I put in DOT 5 and bleed the whole system to wash out the DOT 3.
>
> The car has been up on jack stands while we continue its conversion,
> but the brake fluid level
> has been continually dropping. I have added about 3 oz. to the MC.
>
> The strange thing is I can not find any leak. No puddles. No drips.
> All the wheel cylinders are dry. The MC is dry.
> No brake fluid leaking onto the drivers floor (this has no carpet right
> now.)
> This has been going on for over a month. Where is the brake fluid
> going? Does DOT 5 evaporate?

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