[namba209]

Well the booster will work with no fluid in the MC. It will just make the pedal go to the floor a lot easier. The booster works with a vacuum chamber on the MC side separated from the firewall side by a rubber diaphragm. Whe you apply the brake pedal, ambient air is allowed into the firewall side of the chamber. The pressure differential between ambient air pressure on one side of the diaphragm and vacuum on the other give you a power boost application to the brake pedal action. HTH.