In a message dated 11/5/99 5:43:08 PM Pacific Standard Time,
spaninc@ceibo.entelnet.bo writes:
> Hi folks, here is my last take on clutch bleeding and fluid reuse. First of
> all, there is no reason why "clean" brake fluid can not be recirculated in
> a "clean" system. The fluid does not decompose or interact chemically with
> any other substance and thus remains chemically stable for quite some time.
> The fluid eventually absorbs water and thus losses some of its hydraulic
> properties and is no longer inert to system materials. As far as the fluid
> goes, it does not remain static inside the system. By design hydraulic
> systems are dynamic and every time you press the pedal the fluid moves
> inside the system, interacts with the system walls and moves around itself.
> Recirculating fluid is thus safe as far as the chemistry of the fluid.
Two problems here. First as you have said the fluid absorbs water. Also I'm
not sure I would use the adjective "eventually" to describe the water
absorption properties of brake fluid. This changes the boiling point of the
fluid, and therefore the chemistry of the fluid. (One of the things you deal
with in chemistry is changes of state liquid to gas in this case.) Brake
fluid contains chlorates and chlorine is a very reactive element, so I'm not
to sure about how stable the fluid is. Therefore your statement that this is
safe as far as chemistry goes is not correct. Maybe I'm a little anal about
this, but if you have ever gotten a set of B brakes hot enough to boil the
fluid out of the calipers and have the pedal go to the floor, you might have
a different point of view.
> Lets talk particles, there are three important particles that contaminate
> the system. Oxides from the system, dirt (in the form of dust, soil, etc)
> and micro bubbles. How can you remove these? filtration. I would recommend
> to put a filter on the end of the pipe that goes back into the system from
> the nipple. Since I have access to laboratory materials I have managed to
> use a VW gas tank mesh filter made of polyethylene with Whatman filter
> paper No.1. This step will trap most all dirt of significant size that can
> cause brake problems and also coalesce micro bubbles. I believe that
> flushing the system before doing a serious bleed is of utmost importance.
> Recirculation done safely and properly with a good final filter is possible
> and can be a safe and fast way to bleed your brakes and clutch. Enrique
Why would you go to all this effort? Regardless of you availability of
materials this is a PITA. Also the only reason I could even consider doing
such a procedure would be to save money on brake fluid, so I would have to
ask if you can't afford brake fluid, how are you going to pay for the new
front fenders and hood after the brakes fade and you smack something?
Remember the fluid does not have to saturated for the boiling point to be
lowered. Not to mention that if you have all this tubing running all over the
place you run the risk of spilling a few drops of fluid on the paint
somewhere and finding out first hand just what a great paint remover brake
fluid is. (the Murphy factor)
One last question if this were such a great idea why don't commercial auto
shops, who go through more brake fluid in a week that the people on this list
do in a year, do this? Two reasons, one both car makers or fluid makers say
not to, and second you always going to leave some water in the fluid and
therefore defeat the purpose of flushing the fluid. So unless you can
convince me that you know more about hydraulics that the guy that designed
the system and wrote the repair manual I'm gonna have to say No way.
$.02
Rick Ewald
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