1986 Sdl- Brake Pedal Doesn't Seem To Be Able To Build Pressure- There Is Vacuum At The Hose Coming Fram Vac Pump- Haven't Measured Yet- Pedal Will Build Pressure When Car Is Not Running-all Other Vac Operated Systems Are Working Fine- So My Braking Is Ok, Not Great- Getting A Head Pedal At The Bottom- Culprit May Be Vac Pump Or Maybe The Check Valve?