Hyrdoboost question

I have a hydroboost system in my 69 with a concept one power steering pump, when you press the brakes the unit makes an odd noise.Does anyone know if this could be due to bleeding issues? or maybe the reservoirs to small? There is no power steering on the car.if you remove the oil fill cap on the p/s pump and brakes depressed the fluid does go down a solid inch or so.

heres the pump