RE: Battle of the DOTs

[Brian Schlump <brianjan_64@xxxxxxx>]

I'm slightly confused.  The detailed article states that if water gets 
in a Dot 5 system, it will form a globule that is heavier than the 
fluid, and will sink to the lowest point.  If that's the case, I don't 
understand how cracking the bleeders once a year will remove any water 
that forms.  The bleeders are always in the top of the component in 
order to bleed off any air that is trapped.


chymar01@xxxxxxxxxxx wrote:
> 
> 
> 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. 
> 
> 
> [Non-text portions of this message have been removed] 
> 
> 
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> 
> 
> 
> [Non-text portions of this message have been removed]
> 



'64 Belvedere
Davenport, Iowa

"The difference between ordinary and extraordinary is that little 
extra."


----
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