Amy, et al,
This is in response to your question about the hazards of mixing
glycol-based and
silicone brake fluid.
1. The "experts" say don't mix fluid types. In fact "they" don't
recommend
mixing brands of fluids.
2. I haven't heard of an adverse reaction between the DOT3/4 and DOT5
fluids other
than possible deterioration of performance (i.e. spongy pedal;
dragging brakes.)
3. Many British cars of our vintage used natural rubber seals. In my
experience these
weren't compatible with anything--especially silicone. Swelling or
leaking seals
are the most common problems.
4. You should be able to safely flush the old mix. But I state the
obvious: Check for
leaks and changes in braking performance.
Hope this helps.
DB
Amy Turner wrote:
>
> Frank Clarici wrote:
> >
> > ...Amy is "one of the guys" she drives a Bugeye with a nicly modified 1275,
> > cam, Weber side draught, LCB header, etc. and she drives it at around 90
> > MPH! I know this for a fact.
>
> Ahem. Just once. Really. And that was on a deserted road in the
> middle of the night. Furthermore, a GM experimental car (a Corvette),
> containing a friend, was following me. In case you've heard the rumors,
> they're true. The bonnet can and will fly up once you reach a certain
> speed.
>
> > She will also be the one to inform us as to the mixing capabilities of
> > dot 4 and dot 5 brake fluid.
> > Her Sprite is the current test model to see just how well or if the 2
> > brake fluids mix.
>
> I didn't choose to do this. A trip across the Smokies and back made it
> a necessity. On the return trip the brake pedal started acting funny,
> going down but not coming back up. Yep, low on fluid. A fellow club
> member had brake fluid, but it was dot 5. We had no other choice but to
> pour it in and hope that that was what was already in there. It
> wasn't. Thus far there have been no problems, but I haven't driven the
> car much at all because I'm leery. Can someone tell me (and Frank and
> everyone else I've asked) just why you can't mix dot 4 and dot 5?
> Everyone says they can't be mixed, but no one can tell me why. If dot 4
> does the job and dot 5 does the job and they happen to wind up in there
> together, what horrible thing happens? Do they, in combination, become
> corrosive? Do they lose all sense of what they were intended for and
> magically turn into a gas? Do they explode? Do they bad-mouth me to my
> friends and get me rejected from the finest social circles? What?!
>
> The brakes are still working, but I plan to bleed them and put Castrol
> LMA in there. Unless I replace the entire braking system, I realize
> that a little dot 5 will remain. Will that be a problem?
>
> I also realize that brake fluid doesn't just disappear. The search for
> the leak is on.
>
> > Amy...How are the brakes on Healium? Did you change the fluid yet?
>
> Not just yet, but I spent yesterday moving the project cars into a
> warehouse where I'll work on them over the winter. I would have changed
> the fluid -- and probably the oil, too -- if I hadn't been busy
> transporting cars.
>
> Afraid to be a guinea pig,
> Amy
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