Does Brake Fluid Erode Rubber?
Mitchell Jones
the work drained the old power steering fluid and replaced it with
automatic transmission fluid, after which a new leak appeared, this time
in the power steering pump, which is situated at the lowest point in the
system. At first, I speculated that the ATF had caused the leak, but those
various speculations led nowhere. Finally a fellow suggested that I add
some brake fluid to the system, since it was known to stop leaks in power
steering systems. I tried it, and it worked!
And that brings me to my question: *why* did it work? My guess is that
brake fluid contains an additive which erodes rubber. If there had been an
accumulation of rubber particles in my power steering system (which is 9
years old) due to wear and tear, and if those particles were blocking
leaks in the seals in the power steering pump, which was, as noted above,
situated at the low point in the system, then when the mechanic drained
the old fluid, he probably drained off those particles as well. Result:
the pump began to leak. And if the brake fluid that I added then eroded
away part of the surface of the rubber hose, thereby replacing the rubber
particles that had been sealing the pump, that would explain why adding
brake fluid caused the leak to stop.
So, do any of you know the composition of brake fluid? Is there anything
present that would erode rubber? If so, what is it, and what specific
chemical reactions are involved?
--Mitchell Jones
===============================================
Quotes may have been edited for appropriateness. Killfile
inmates: Mark Mallory, John_justjohn, Cliff Frost.
Mark Tarka
>
> I recently had a leaky power steering hose replaced. The mechanic who did
> various speculations led nowhere. Finally a fellow suggested that I add
> some brake fluid to the system, since it was known to stop leaks in power
> steering systems. I tried it, and it worked!
Google: power steering leak brake fluid
It checks-out, but with warnings. I'm gonna try it.
> And that brings me to my question: *why* did it work? My guess is that
> brake fluid contains an additive which erodes rubber. If there had been an
[snip]
> particles that had been sealing the pump, that would explain why adding
> brake fluid caused the leak to stop.
Probably causes old seals to swell and seal better. Ever notice
how black old brake fluid is...and how clear when new?
> So, do any of you know the composition of brake fluid? Is there anything
> present that would erode rubber? If so, what is it, and what specific
> chemical reactions are involved?
Google: brake fluid msds
> Quotes may have been edited for appropriateness. Killfile
> inmates: Mark Mallory, John_justjohn, Cliff Frost.
A mutual admiration society?
Mark
Frank Logullo
"Mitchell Jones" <mjo...@jump.net> wrote in message
news:mjones-0901...@jump-tnt-0135.customer.jump.net...
> I recently had a leaky power steering hose replaced. The mechanic who did
> the work drained the old power steering fluid and replaced it with
> automatic transmission fluid, after which a new leak appeared, this time
> in the power steering pump, which is situated at the lowest point in the
> system. At first, I speculated that the ATF had caused the leak, but those
> various speculations led nowhere. Finally a fellow suggested that I add
> some brake fluid to the system, since it was known to stop leaks in power
> steering systems. I tried it, and it worked!
>
> And that brings me to my question: *why* did it work? My guess is that
> brake fluid contains an additive which erodes rubber. If there had been an
> accumulation of rubber particles in my power steering system (which is 9
> years old) due to wear and tear, and if those particles were blocking
> leaks in the seals in the power steering pump, which was, as noted above,
> situated at the low point in the system, then when the mechanic drained
> the old fluid, he probably drained off those particles as well. Result:
> the pump began to leak. And if the brake fluid that I added then eroded
> away part of the surface of the rubber hose, thereby replacing the rubber
> particles that had been sealing the pump, that would explain why adding
> brake fluid caused the leak to stop.
>
> So, do any of you know the composition of brake fluid? Is there anything
> present that would erode rubber? If so, what is it, and what specific
> chemical reactions are involved?
>
power steering fluids appear to be mostly hydrocarbons. This I gathered by
scanning MSDS's but most of these things are mixtures and not all
ingredients disclosed. Don't know effect on rubber. Lot of things will
swell rubber which helps seals but then, I guess, could cause problems.
Frank
Michael David Hamilton
: So, do any of you know the composition of brake fluid? Is there anything
: present that would erode rubber? If so, what is it, and what specific
: chemical reactions are involved?
: --Mitchell Jones
The composition of brake fluid has already been commented upon.
I don't think brake fluid attacks rubber, because many of the
components in brake systems use rubber seals, in fact if one get
hydrocarbons in the brake system it will lead to seal failure.
Mike
a-s
NOT to attack the rubber components in the braking system. The ATF fluid
probably contains mineral oil which will swell and soften some rubbers. I
await suggestions on why the brake fluid helps. Sounds like witchcraft to
me.
alan
"Mitchell Jones" <mjo...@jump.net> wrote in message
news:mjones-0901...@jump-tnt-0135.customer.jump.net...
Mitchell Jones
> Mitchell Jones wrote:
> >
> > I recently had a leaky power steering hose replaced. The mechanic who did
> [snip]
> > various speculations led nowhere. Finally a fellow suggested that I add
> > some brake fluid to the system, since it was known to stop leaks in power
> > steering systems. I tried it, and it worked!
>
> Google: power steering leak brake fluid
>
> It checks-out, but with warnings. I'm gonna try it.
>
> > And that brings me to my question: *why* did it work? My guess is that
> > brake fluid contains an additive which erodes rubber. If there had been an
> [snip]
> > particles that had been sealing the pump, that would explain why adding
> > brake fluid caused the leak to stop.
>
> Probably causes old seals to swell and seal better.
***{You appear to be correct. I found a spec for SAE J1703 (DOT 3) brake
fluid which states that it softens rubber and causes it to swell. (See
www.wd-wpp.com/chemicals/chems011.pdf.) I still don't know *how* it does
that, however. (Yeah, I know: "Why ask why?" :-) --MJ}***
Ever notice
> how black old brake fluid is...and how clear when new?
***{True, but that's likely due to the fact that the old brake fluid has
become contaminated with fine particles due to wear on moving parts, which
would happen whether the rubber swelled or not. --MJ}***
> > So, do any of you know the composition of brake fluid? Is there anything
> > present that would erode rubber? If so, what is it, and what specific
> > chemical reactions are involved?
>
> Google: brake fluid msds
***{Looking at a number of the "material safety data sheets" (e.g.,
http://library.cbest.chevron.com/lubes/ehlchevmsdsv9.nsf/a37a566cb6e34c88882569cf0002e997/98b0c0b7a9fbbbf0882569b5000bdece?OpenDocument),
it appears that DOT 3 brake fluid consists primarily of ethanol and
ethylene glycol (i.e., grain alcohol and antifreeze), plus some oxydation
and corrosion inhibitors.
Looking at http://www.ethanolrfa.org/factfic_enperf.html, I found the following:
"When ethanol was first introduced in the early 1980s, some cars
experienced deterioration of some elastomers (rubber-like parts) and metal
in fuel system components. Very quickly manufacturers upgraded these fuel
system components so that today they are all compatible with ethanol
fuels."
The above strongly suggests that elastomers in the power steering system
would be subject to deterioration if exposed to ethanol.
Since the ethanol causes elastomers to deteriorate, I assume it is the
ethylene glycol that softens them and causes them to swell, thought I
haven't yet found anything proving that.
In addition, I still have no idea *why* or *how* the swelling, softening,
or deterioration comes about--which, of course, was the main thing I was
interested in.
--Mitchell Jones}***
> > Quotes may have been edited for appropriateness. Killfile
> > inmates: Mark Mallory, John_justjohn, Cliff Frost.
>
> A mutual admiration society?
***{Or the reverse. :-) --MJ}***
> Mark
===============================================
Quotes may have been edited for appropriateness. Killfile inmates:
Mark Mallory, John_justjohn, Cliff Frost, Lynn Kurtz.
Bruce Hamilton
> Finally a fellow suggested that I add some brake fluid to the system,
> since it was known to stop leaks in power steering systems.
> I tried it, and it worked!
That trick has been around for many decades, but probably won't be
around for many more, as the system composition is changing. Power
steering fluids and automatic transmission fluids are blended
hydrocarbon formulations ( 85 - 90 % lubricant base grade ) which
are also expected to swell elastomeric hoses and seals. Consequently,
seal materials and hoses are permitted to swell about 10%, with some
associated softening, but they are not allowed to harden or shrink
seals.
Traditional brake fluids ( glycol ethers ) are being replaced by
borate ester or silicon-based fluids. Brake fluids are also not
allowed to greatly swell ( ~>10% ) the elastomers found in brake systems,
which are often made with different elastomers in fluid contact to
those used for systems ( such as power steering ) using mineral oil
based fluids.
There can be synergistic effects if different fluids are mixed,
( ATF could swell seals 5%, brake fluid could swell the same
seals 10%, but a mixture swells them 15% ). The problem with
blending fluids to obtain increased swelling is that such swelling
greatly weakens the elastomers, and most dynamic seals will
abrade/wear much quicker, as the tear strength is greatly reduced
as swelling increases.
The elastomer hardness is also decreased with swelling, so changes
of hardness may also be specified after immersion testing of
elastomers with fluids.
The fluids effectively partially dissolve in the elastomer, thus
swelling it, and most moving elastomeric seals already have a certain
% of swelling incorporate in the design. As we move to more sophisticated
elastomers for fluid contact, such as fluorocarbons, the design
swelling is much lower, and many traditional fluid blends have
little effect.
In general, it's best to replace seals when worn, rather than create
complex mixtures to put off the inevitable service. Most of the
major elastomer companies, such as Gates, are likely to have detailed
information.
Bruce Hamilton