Re: Battle of the DOTs

[Herb <zephyr9900@xxxxxxxxxxx>]

I beg to differ with you but 5 is not miscible with 3 or 4!  Federal Law can
say all it wants to it's still chemically not compatible also DOT 5 is not
an on the shelf item unless you go to a speciality store like speed shops
and the like and I don't recall seeing it on the shelf their.  Unless your
happy with as the article said (create a gelatin like goop which will
attract more crud and eventually plug up metering orifices or cause pistons
to stick.) Sup to you!  I speak from experience, I work for the government
and started with them twisting wrenches many years ago and we used DOT 5 in
all our vehicles every single time we had one out being worked on by a
civilian contractor and they serviced it they put DOT 3 in, shortly their
after it had brake problems every time.  Pull the MC cover and you had a
glob of sludge and we would get a rag clean the master out and power bleed
the system till it ran purple blue or red or what ever color the DOT 5 was
at the time.  O, and this was on cars that were less than 6 or 7 months old
so you can't blame crud in the system.  One point of the letter I would
dispute about bleeding, water lays on the bottom of the wheel cylinder and
or caliper and when you bleed, your bleeding from the top because air goes
to the top.  So unless you remove your calipers and wheel cylinders and
rotate them upside down and bleed the water stays at the bottom fluid and
air go out the top.  The problem we did have was on low mileage older
vehicles in the fleet, the wheel cylinders and calipers would eventually
have rust form on the bottom surface and act like sand paper and eventually
cause leaks necessitating rebuild or replacement.  Kind of sounds like the
scenario of a lot of our cars that sit for Long periods of time.

    
 Herb 
 
1959 Coronet 326 Poly
1963 Fury 2D/HT 6.1
1963 Sport Fury Convertible 361
1970 Challenger RT 440
1999 Durango SLT 5.9
2006 300-C Heritage 5.7
2008 SRT-8 Magnum 6.1
St. Louis, MO.
 
 
-------Original Message-------
 
From: chymar01@xxxxxxxxxxx
Date: 3/11/2009 6:31:39 PM
To: 1962to1965mopars@xxxxxxxxxx
Subject: Re: Battle of the DOTs
 
 
While I understand what the article is saying about attracting the crud in
the system when DOT 5 is introduced(section #4), the fact remains that the
fluids themselves are fully miscible. Federal law requires that all brake
fluids sold in the US must be able to work with each other. That way, if
someone needs fluid NOW, they can use whatever is on the shelf.
It is recommended that when switching to DOT 5 that it be done when
replacing the brake system components all at once. I wouldn't switch
otherwise. And definitely crack the bleeders at least once a year like it
says below.
 
 
----- Original Message -----
From: "Herb" <zephyr9900@xxxxxxxxxxx>
To: "1962 to 1965 Mopars" <1962to1965mopars@xxxxxxxxxx>
Sent: Wednesday, March 11, 2009 5:54:07 PM GMT -05:00 US/Canada Eastern
Subject: Battle of the DOTs
 
 
 
FYI if any one wants to read it! Her it is.
 
Battle of the DOTs
DOT 3-4 Verses DOT 5. Which brake fluid should I use?
"With regards to the DOT 3-4 verses DOT 5 brake fluid controversy, here is
an article sent to me by Mr. Steve Wall. It is one of the most professional
treatments I have seen on the subject".
[I had to condense this article from 6 pages to 1 due to space limitations.
Brake Fluid Facts
by Steve Wall
As a former materials engineering supervisor at a major automotive brake
system supplier, I feel both qualified and obligated to inject some material
science facts into the murky debate about DOT 5 verses DOT 3-4 brake fluids.
The important technical issues governing the use of a particular
specification brake fluid are as follows:
1. Fluid compatibility with the brake system rubber, plastic and metal
components.
2. Water absorption and corrosion.
3. Fluid boiling point and other physical characteristics.
4. Brake system contamination and sludging.
Additionally, some technical comments will be made about the new brake fluid
formulations appearing on the scene.
First of all, it's important to understand the chemical nature of brake
fluid. DOT 3 brake fluids are mixtures of glycols and glycol ethers. DOT 4
contains borate esters in addition to what is contained in DOT 3. These
brake fluids are somewhat similar to automotive anti-freeze (ethylene
glycol) and are not, as Dr. Curve implies, a petroleum fluid. DOT 5 is
silicone chemistry.
Fluid Compatibility
Brake system materials must be compatible with the system fluid.
Compatibility is determined by chemistry, and no amount of advertising,
wishful thinking or rationalizing can change the science of chemical
compatibility. Both DOT 3-4 and DOT 5 fluids are compatible with most brake
system materials except in the case some silicone rubber external components
such as caliper piston boots, which are attacked by silicon fluids and
greases.
Water absorption and corrosion
The big bugaboo with DOT 3-4 fluids always cited by silicone fluid advocates
is water absorption. DOT 3-4 glycol based fluids, just like ethylene glycol
antifreezes, are readily miscible with water. Long term brake system water
content tends to reach a maximum of about 3%, which is readily handled by
the corrosion inhibitors in the brake fluid formulation. Since the
inhibitors are gradually depleted as they do their job, glycol brake fluid,
just like anti-freeze, needs to be changed periodically. Follow BMW's
recommendations. DOT 5 fluids, not being water miscible, must rely on the
silicone (with some corrosion inhibitors) as a barrier film to control
corrosion. Water is not absorbed by silicone as in the case of DOT 3-4
fluids, and will remain as a separate globule sinking to the lowest point in
the brake system, since it is more dense.
Fluid boiling point
DOT 4 glycol based fluid has a higher boiling point (446F) than DOT 3 (401F)
and both fluids will exhibit a reduced boiling point as water content
increases. DOT 5 in its pure state offers a higher boiling point (500F)
however if water got into the system, and a big globule found its way into a
caliper, the water would start to boil at 212F causing a vapor lock
condition [possible brake failure -Ed.]. By contrast, DOT 3 fluid with 3%
water content would still exhibit a boiling point of 300F. Silicone fluids
also exhibit a 3 times greater propensity to dissolve air and other gasses
which can lead to a "spongy pedal" and reduced braking at high altitudes.
DOT 3 and DOT 4 fluids are mutually compatible, the major disadvantage of
such a mix being a lowered boiling point. In an emergency, it'll do.
Silicone fluid will not mix, but will float on top. From a lubricity
standpoint, neither fluids are outstanding, though silicones will exhibit a
more stable viscosity index in extreme temperatures, which is why the US
Army likes silicone fluids. Since few of us ride at temperatures very much
below freezing, let alone at 40 below zero, silicone's low temperature
advantage won't be apparent. Neither fluids will reduce stopping distances.
With the advent of ABS systems, the limitations of existing brake fluids
have been recognized and the brake fluid manufacturers have been working on
formulations with enhanced properties. However, the chosen direction has not
been silicone. The only major user of silicone is the US Army. It has
recently asked the SAE about a procedure for converting from silicon back to
DOT 3-4. If they ever decide to switch, silicone brake fluid will go the way
of leaded gas.
Brake system contamination
The single most common brake system failure caused by a contaminant is
swelling of the rubber components (piston seals etc.) due to the
introduction of petroleum based products (motor oil, power steering fluid,
mineral oil etc.) A small amount is enough to do major damage. Flushing with
mineral spirits is enough to cause a complete system failure in a short time
I suspect this is what has happened when some BMW owners changed to DOT 5
(and then assumed that silicone caused the problem). Flushing with alcohol
also causes problems. BMW brake systems should be flushed only with DOT 3 or
4.
If silicone is introduced into an older brake system, the silicone will
latch unto the sludge generated by gradual component deterioration and
create a gelatin like goop which will attract more crud and eventually plug
up metering orifices or cause pistons to stick. If you have already changed
to DOT 5, don't compound your initial mistake and change back. Silicone is
very tenacious stuff and you will never get it all out of your system. Just
change the fluid regularly. For those who race using silicone fluid, I
recommend that you crack the bleed screws before each racing session to
insure that there is no water in the calipers.
New developments
Since DOT 4 fluids were developed, it was recognized that borate ester based
fluids offered the potential for boiling points beyond the 446F requirement,
thus came the Super DOT 4 fluids - some covered by the DOT 5.1 designation -
which exhibit a minimum dry boiling point of 500F (same as silicone, but
different chemistry).
Additionally, a new fluid type based on silicon ester chemistry (not the
same as silicon) has been developed that exhibits a minimum dry boiling
point of 590F. It is miscible with DOT 3-4 fluids but has yet to see
commercial usage.
 
   
Herb
 
1959 Coronet 326 Poly
1963 Fury 2D/HT 6.1
1963 Sport Fury Convertible 361
1970 Challenger RT 440
1999 Durango SLT 5.9
2006 300-C Heritage 5.7
2008 SRT-8 Magnum 6.1
St. Louis, MO.
 
 
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Please address private mail -- mail of interest to only one person --
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as well as other personal messages only to the intended recipient, not to
the Clubhouse public address. This practice will protect your privacy,
reduce the total volume of mail and fine tune the content signal to Mopar
topic.  Thanks!
 
'62 to '65 Mopar Clubhouse Discussion Guidelines:
http://www.1962to1965mopar.ornocar.org/mletiq.html.
 
 
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