[Chrysler300] DOT Choice

[Herb <zephyr9900@xxxxxxxxxxx>]

With all the talk about brakes and fluids, All I can say is your looking for
trouble with DOT 5.  Once you change over you cant go back unless you
replace EVERY rubber part in your brake system.  Dot 4 does every thing DOT
5 does except contaminate the system with silicone, unless you live on the
north or south pole, or are running a dedicated race car, DON'T DO IT. 
Extreme and I mean Extreme heat or cold conditions are all that I can
justify the use of DOT 5.  I worked for the government and converted
hundreds of vehicles over to DOT 5, that experience is the reason I wont do
it to my cars.  We kept consistently busy fixing DOT 5 related brake
problems.  The only reason they do change to DOT 5 is any vehicle can
potentially go to any place in the world at any time, or that is the logic
in the manual.  I know, I know DOT 5 wont absorb moisture, that is correct
but were does the moisture go???  O ya water is heaver than DOT 5, down to
the bottom of the wheel cylinders and calipers to stay, and that is why they
start leaking from the corrosion on the sealing serfaces.  If you completely
purge or bleed your brake system every 30,000 or 35,000 like your supposed
to, you will never have corrosion problems with DOT 3 or 4 because the
moisture that is absorbed by the DOT 3 is gone when you do a system bleed.. 
Problem is no one ever purges the system, out of sight out of mind until you
have brake problems, Same with Transmissions, no one changes fluid & filter
or thinks about it till a problem arises and by then it's tooooo late.  O,Ya
when you bleed DOT 5 were does the moisture go? OOps, it is still at the
bottom of the wheel cylinders and calipers because it is not absorbed and is
heaver than DOT 5!!  That said this is not an overnight problem with any
brake fluid, most of our cars are forty five years old or older and the
brake problems are just showing up.  Actually I think the moisture that is
absorbed, is really a good thing if you service your system on a regular
basis.  That is why I invested in a power bleeder, about every five or six
years I purge the systems on my cars and never have any problems other than
replacing shoes or pads.  Here is an article that is good information.  This
is just my $00.02 worth from experience, and I know everyone has a
conflicting opinion, this is just mine.
 
 
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 
 
1956 Plymouth Belvedere 361 4-Sale
1959 Coronet 326 Poly
1961 Belvedere Custom Suburban 318 Poly
1962 Dodge Dart 225 Slant Six  4-Sale
1963 Fury 2D/HT 6.1L
1963 Sport Fury Convertible 361
1970 Chrysler 300 Hurst 440
1999 Durango SLT 5.9L
2008 SRT-8 Magnum 6.1L
St. Louis, MO.

[Non-text portions of this message have been removed]



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