The problem i had with removing the air from the tank was because i tried to simplify the procedure which is somewhat complicated.
The oil tank needs a third hole for venting which might cause oil spills.
The piston/servo method does not need the tank actually and because the piston actually changes the volume it does not create
any ill effects.
The pump does not change its volume so when it pushes the oil and the wheel brake pistons move it creates a vacuum in the tank.
Basically a check valve is needed that will allow the tank to be vented.
I could also connect the check valve in line with the return line so the oil can only go from the pump's output to the tank and not both ways because of the pressure reduction inside the tank.
I now think that this system with the electric pump is too complicated, heavy and expensive and does nothing better than the piston/servo system.
My conclusion is that Hydraulic brakes are the way to go if someone wants true proportional brakes by using only the piston/servo system
and the air brakes are better if someone wants a simple and clean
system.
Chris