At 08:03 AM 8/9/98 -0400, Dave Iwansky <baldycotton@pop.mindspring.com> wrote:
>.... My hoses appear to be replacements (MGA) but it definately has DOT5
silicone fluid. I have always thought that the pedal felt a tad too spongy,
but my PO said that it was normal for silicone, but now 'm wondering (per
Chip) if there are indeed air bubbles mucking about in there.
>
>I'm in the process of rasslin' with new front disks, so based on your
advice (both of you) it looks like it's time to go to Castrol GT/LMA.
>
>I'd be .... greatful if one of yous guys would give the whole rundown on
what to do and how to do it.
Okay, here's the $.02 on brake fluid according to barneymg. When I
restored my car I replaced all the hydraulic parts with new. Thereafter
I've been using DOT-5 fluid continuously for 12 years and 127,000 miles
with no brake fluid problems whatsoever (except maybe slightly soft pedal,
but I have a heavy foot, so I'd never notice that anyway). Nada, none,
zip! I still have the same master and wheel cylinders and clutch slave and
hoses and pressure switch, all working flawlessly with DOT-5 fluid.
But I do religiously flush new fliud through the system at least every two
years to get tho old deteriorated crap out of there. I believe that if you
do this, the system will give you very long and trouble free service
regardless of what fluid you use. I have seen well cared for cars go for
30 years on the original hydraulic components (although I wouldn't
recommend it). I would not, however, risk using the mineral based version
of DOT-3 fluid with natural rubber seals. And since I'm not sure which
DOT-3 fluids may be mineral based, or which rubber seals may be natural
rubber, I think I will never use DOT-3 fluid in any LBC. And IMHO, you are
likely to buy yourelf trouble big time if you switch fluid types while
leaving the old rubber bits in the system.
I am however about to change out (renew) all of the rubber parts in the
hydraulic system just on general principals (127K miles is general enough),
especially concern for the health of the flex hoses. When I do this, I
plan on switching over to Casterol GT/LMA DOT-4 fluid. WHY? Because:
(1) I'd like to find out for myself if the difference in pedal feel is
significant.
(2) DOT-4 fluid is less expensive.
(3) DOT-4 fluid is now more readily available than it was 12 years ago.
(4) I now have confidence that with all fresh rubber bits in the system
and good maintainance I will not be spilling brake fluid on the paint in
the forseeable future
(5) I'm not concerned about the higher temperature capability of DOT-5
for racing applications (only with frequent flushings).
And how to go about changing the type of hydraulic fluid:
(1) Resolve yourself to changing out every bit of rubber in the entire
system when you switch fluids, and procure all of the parts in advance of
the job.
(2) Flush the entire system with denatured alcohol before installing the
new fluid. I believe the easiest way to do this is to do it before you
disassemble anything. Remove as much of the old fluid as possible from the
master cylinder, fill with the alcohol, and bleed the brakes in the normal
manner until nothing comes out but clean alcohol at every bleed fitting.
You will likely need at least two quarts of alcohol to do this. Then blow
out the lines with compressed air, remove the flex hoses and all rubber
packing, blow out the cylinders and steel lines again with compressed air,
and let the system air dry for at least a few hours.
(3) Then install the new flex hoses and all the rubber packing kits (or
new cylinders), add the new fluid, and bleed the system in the normal
manner until all air is out and nothing but clean fluid comes through every
bleed fitting.
(4) I still like my Eezibleed kit for a big job like this. The trick is
to be sure that you have a pressure tight seal at every little hose fitting
and where the cap screws onto the brake reservoir, so you don't blow fluid
all over the place. And I've never had any trouble using 30 psi pressure
direct from a car tire without reduction. I think you would have the best
luck with an Eezibleed if you set it up for use with just one type of brake
reservoir screw cap, test with air pressure only before putting in the
fluid, and when you get it to work properly don't ever switch the screw cap
to anything else, just leave well enough alone.
That ought to do it.
Barney Gaylord
1958 MGA with an attitude
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