Originally Posted by zip439

Guys I do not get what you are saying on vacuum. Vacuum in the line going to the brakes comes off the intake manifold and that vacuum varies with the position of the throttle plate. When the car is at idle the vacuum increases because the throttle plate closes. When you are cruising down the road vacuum reading is considerable lower because throttle plate is open. When you apply the brakes your foot should be off the throttle, throttle plate closes and vacuum increases to the brakes through the line connected to the master cylinder. You have greater vacuum measured in inches of vacuum (-Hg) at idle than at open throttle cruising down the road.