Date:         Thu, 06 Jul 95 14:16:11 CDT
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         Joel Walker <JWALKER@ua1vm.ua.edu>
Subject:      brake fluid info

while lurking on another car list (for a non-access acquaintance), i ran
across this ... it might be of some use to older buses as well.

                                  Brake Fluids

                              by Kenneth Streeter,
                        with input from various sources
-----------------------------------------------------------------------------

The discussion of whether to use DOT3, DOT4, or DOT5 brake fluids in
Triumphs is a common topic. The information provided herein should
help you to decide which of these brake fluids are best for you and
your car.  I would point out that I am not an "expert" on the topic,
but have collected the experiences of many other Triumph enthusiasts,
as well as opinions of professional auto restorers.  I have tempered
my findings with my own experiences and opinions.

DOT3

  DOT3 brake fluid is the "conventional" brake fluid used in most
  vehicles.  One of the most familiar brands is "Prestone."

  Advantages:
    o  DOT3 fluid is inexpensive, and available at most gas stations,
       department stores, and any auto parts store.
  Disadvantages:
    o  DOT3 fluid eats paint!
    o  DOT3 fluid absorbs water very readily. As such, once a
       container of DOT3 has been opened, it should not be stored
       for periods much longer than a week before use.
    o  Since DOT3 fluid absorbs water, any moisture absorbed by the fluid
       can encourage corrosion in the brake lines and cylinders.

DOT4

  DOT4 brake fluid is the brake fluid suggested for use in late model
  Triumphs. The most familiar brand is "Castrol GT-LMA"

  Advantages:
    o  DOT4 fluid is available at most auto parts stores, and at some (but
       not all) gas stations or department stores.
    o  DOT4 fluid does not absorb water as readily as DOT3 fluid.
  Disadvantages:
    o  DOT4 fluid eats paint!
    o  DOT4 fluid is generally about 50% more expensive than DOT3 fluid.
    o  Since DOT4 fluid still absorbs some water, any moisture absorbed by
       the fluid can encourage corrosion in the brake lines and cylinders.

DOT5

  DOT5 brake fluid is also known as "silicon" brake fluid.

  Advantages:
    o DOT5 doesn't eat paint.
    o DOT5 does not absorb water and may be useful where water absorption
      is a problem.
    o DOT5 is compatible with all rubber formulations. (See more on this
      under disadvantages, below.
  Disadvantages:
     o DOT5 does NOT mix with DOT3 or DOT4. Most reported problems with DOT5
       are probably due to some degree of mixing with other fluid types. The
       best way to convert to DOT5 is to totally rebuild the hydraulic
       system.
    o  Reports of DOT5 causing premature failure of rubber brake parts were
       more common with early DOT5 formulations. This is thought to be due
       to improper addition of swelling agents and has been fixed in recent
       formulations.
    o  Since DOT5 does not absorb water, any moisture in the hydraulic
       system will "puddle" in one place. This can cause localized corrosion
       in the hydraulics.
    o  Careful bleeding is required to get all of the air out of the
       system. Small bubbles can form in the fluid that will form large
       bubbles over time. It may be necessary to do a series of bleeds.
    o  DOT5 is about twice as expensive as DOT4 fluid. It is also difficult
       to find, generally only available at selected auto parts stores.

General Recommendations:

  1.  If it works for you, use it. You won't hurt anything if you do the
      conversion correctly.  (generally by replacing all sealing
      components in the brake system.)
  2.  If you have a brake system that doesn't leak or show any other
      signs of failure, but has old seals in it, don't change fluid types
      as a result of reading this article.  If it isn't broken, don't
      "fix" it  -- you may simply break it instead!
  3.  DOT3 is an adequate brake fluid for use in Triumphs, although it is
      rarely preferred.
  4.  DOT4 fluid, for a slight increase in cost, will give significantly
      increased resistance to moisture absorption, thus decreasing the
      likelihood of corrosion compared to DOT3.
  5.  DOT4 fluid has a higher boiling point than DOT3, making it
      preferable for high performance uses such as racing, autocross,
      or excessive use of the brakes in mountainous areas.
  6.  DOT5 is a good choice for the weekend driver/show car. It doesn't absorb
      water and it doesn't eat paint. One caveat is that because it doesn't
      absorb water, water that gets in the system will tend to collect at low
      points. In this scenario, it would actually be promoting corrosion!
  7.  DOT5 is probably not the thing to use in your race car although it is
      rated to stand up to the heat generated during racing conditions. The
      reason for this recommendation is the difficult bleeding
      mentioned above.
  8.  Flushing of the brake system every couple years to remove any
      absorbed or collected water is probably a good idea to prevent
      corrosion.
  9.  As always, your experiences may vary!