Alan :
As someone else has pointed out, 'modern' cars use a rubber diaphragm to
allow for differing fluid levels, without exposing the fluid to air.
However, AFAIK these didn't come into common use in the US until roughly
1970. My 62 Chevy and 65 Olds didn't have them, but Dad's 72 Buick did.
I'd guess the main reason was that maintenance costs were not yet an issue.
Periodic changing of brake fluid was just one of those things that the
'cognoscenti' knew to do, and everyone else just waited until they had a
problem. Brake problems were much more common then, but fortunately they
usually failed 'softly', and you could limp home by pumping the pedal. I
vividly remember riding with my baby sitter when she was driving her car to
the shop for a much-needed brake job. (Seems her mother-in-law was riding
in the front center, and tried to "help" her put on the brakes. Hit the
accelerator instead. Left rear tire left a pile of rubber on the road,
after babysitter steered into a phone pole <g> No one hurt, except I bit
my lip.)
My recollection is that dual-circuit brakes came in about the same time, so
maybe it's more a case of people deciding that not having brakes fail was
worth spending some more money on. I seem to recall some DOT safety
standards that addressed the issue, but I'm not certain. My 70 Audi had
dual-circuit, but not the diaphragm.
I don't know when Lockheed and Girling got the message, but I'll bet it was
real close to when the US said "If you don't, we won't buy your cars" <g>
Randall
On Wednesday, March 24, 1999 10:28 PM, Alan Myers
[SMTP:reagntsj@ricochet.net] wrote:
>
> All foolin' aside, I think you'll find all brake fluid reservoirs have
> some form of venting. If they didn't, the rising and dropping levels of
> fluid (or fluif, as it is better known on the list) would form either
> mild compression or vacuum inside the reservoir, one of which could
> possibly cause a shoe or pad to drag, the other could draw air into the
> system through any "weak point". The levels have to rise and drop as you
> apply the brakes, as the shoes and pads wear, and as temperatures vary.
> But, hey, I ain't no engineer!
>
> Alan Myers
> San Jose, Calif.
> '62 TR4 CT17602L
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