[T3] Fuel Pumps & Master Cylinders

[Jim Adney]

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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