[jclark003]

I believe that is the sight glass for the fluid level in reservoir. You should have a cap on top of tank that allows fluid to be added. Not sure what level is full, probably 3/4 or so with all cylinders in down position, definitely do not fill to top. Possible you have a stuck or faulty valve on the engine hatch circuit. Does the hatch lower by itself after the pump shuts off? You should be able to swap valves around to determine if one is bad. Some past posts contain the manufacture name if you need to chase down parts.