At 9:20 PM 3/12/96, Don Taskey wrote:
>First, don't consider Dot 5. It's silicon and must be used with a clean
>system (no old fluid at all, anywhere!). Even after flushing the system
>several times with alcohol, some of the old fluid will remain and mix
>with the silicon to form bondo.
Hm, I have to disagree here.
The problem with mixing DOT3/4 and DOT5 is that they won't mix with each
other. The result of this is that if there is left-over DOT4 in the system
it will form little "bubbles" of DOT 4 in the pipes and cylinders. Any
water or contaminants in the DOT 4 are now trapped in the bubble, where
they will either corrode your pipes or vaporize under braking heat, as
required to make your life difficult.
I've been using DOT5 in a TR3 for some years now, because it seemed less
likely to corrode the (single-circuit, no mistakes please) braking system.
I rebuilt all of the cylinders, replaced the flex hoses, and flushed the
pipes with dry air and DOT5 before installing the working fluid - which
sounds like a lot of work but took just about a day. One problem is that
DOT5 will fill with air bubbles if given half a chance, so you need to pour
it into the system slowly, perhaps by letting the fluid run down a metal
plate or rod instead of just dumping it in, and then you need to bleed the
thing to death.
After all that, I'm quite happy with it in this car. I wouldn't use it in
something I drove really hard, though, difficult to get -all- the air out
of the system with DOT5, which has to affect braking performance some.
John Wroclawski
jtw@lcs.mit.edu
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