[T3] Fuel Pumps & Master Cylinders
Jim Adney
jadney at vwtype3.org
Thu Apr 2 07:03:21 PDT 2020
On 1 Apr 2020 at 19:16, Keith Park wrote:
> YIKES! Looks like they used water for their brake fluid
> and for the gas too...
DoT-3 and 4 slowly absorb water from the air around us, eventually leading
to heavily water contaminated brake fluid. This happens even in areas we
would consider arid. Water-soaked brake fluid becomes corrosive, as shown
in this photo, and also comes down in boiling point, making it more and more
likely that the brake fluid will boil, leading to brake failure. (Boiling means
that there is now vapor in your system, which is the same as driving with a
system that you didn't bother to bleed. Pedal goes to the floor and no
braking happens.)
This is why you should either flush your brake system with fresh DoT 3 or 4
every few years, or switch to DoT-5, which does not absorb water.
Water gets in our gas tanks in two different ways. For '68 and later Type 3s,
a cracked overflow hose allows wheelspray to throw water and dirt into the
gas tank. That can easily add a quart or so of water to your tank in just a few
minutes of driving on wet roads. The water sinks to the bottom, collects
there, and eventually ends up in the lowest place in the system: the FI fuel
pump.
Cars stored for a long time experience condensation in the gas tank. As the
barometric pressure changes, the tank "breaths" outside air in and out.
When the air is humid and the nights are cool, the humidity condenses in the
tank and ends up on the bottom. This process is slow, but over time it is
inevitable and relentless.
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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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