Thanks for all the e-mails on brake fluid, seals and stuff here is some
further detail.
The earliest brake fluids were made from castor oil mixed with alcohol and
were compatible with 'natural' rubber used for hydraulic seals - source
CASTROL.
The castrol brand name was derived from the use of castor oil - source Ferodo.
By 1950 petrochemical fluides such as glycol ethers/polygylcols replaced
earlier types and could be used with the old type seals and the fluids were
compatible - source CASTROL.
DOT 3 fluid should be replaced every 12 months, DOT 4 fluid every 18 months -
source CASTROL (this is for the purpose of fluid performance)
DOT as a standard or spec comes from the USA (Federation of Motor Vehicle
Safety Standards Department Of Transport. There are other standards such as
ISO4925 (DOT 3 with additional requirement in respect of rubber cups, ISO
natural type - source AP Lockheed) and SAE J1703 - source CASTROL.
Some truck makers specify DOT 3 fluid instead of DOT 4 because DOT 3 has
better antiwear properties ideal for heavy clutch use on high mileage vehicles
- source CASTROL
AP Lockheed Universal DOT 3 is ideal for cars (the Spridget?) other than
those where DOT 4 was specified as original fill - source AP Lockheed.
Universal DOT 3 (AP)contains a special lubricating additive which maximises
service life and makes it suitable for use with the latest seal and hose
materials - source AP Lockheed (published 1993).
The Lockheed Hydraulic Brake Company introduced hydraulic brakes into Britain
in 1925 - source AP Lockheed.
AP Lockheed Super 105 fluid confirms to DOT 3 standard and its lab test on
rubber cups (ISO Natural type) is superior to the DOT 3 standard - source AP
Lockheed.
I checked the correct bleed sequence and it does vary a little depending on
master cylinder type and brake type ie drum/drum, disc/drum - source Lucas
Girling.
On production cars, hydraullically operated four wheel brakes were first
fitted (it means first use of hydraulic brakes really) to the American
Dusenburg Model A in 1921- source not readily identifiable put probably
Girling.
Summary, maybe in the USA the ISO4925 spec is a better guide than the more
universally known DOT standard. Use Lockheed or Castrol DOT 4 fluid if in
doubt. The RUDE people (there was only one in fact but the address looked
more like a company than an individual so I used the plural) may have a better
understanding why a short answer is sometimes used in preference to a long
one. I would like to hear of any more brands in the USA that are known to
cause difficulties and of what spec they were - the ISO and J. Nothing I
researched this evening indicated a problem between neoprene and natural
rubber seals and DOT 3 fluids but given time I will research further.
Finally, thanks for the encouraging e-mails.
Daniel
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