Check of Internal Binding. Release problems, hard pedal, and dragging (slow releasing) brakes can all be caused by internal binding. To test a vacuum unit for internal binding, place the transmission/ transaxle in neutral and start the engine. Increase engine speed to 1,500 rpm, close the throttle, and completely depress the brake pedal. Slowly release the brake pedal and stop the engine. Remove the vacuum check valve and hose from the vacuum assist unit. Observe for backward movement of the brake pedal. If the brake pedal moves backward, there is internal binding and the unit should be replaced