Oil Pressure Gauge - Plastic Tube Removal

if you dont have oil in that tube then you are probably out of oil in the engine ...LOL Seriously thats the oil pressure line and you have a mechanical oil pressure guage. Oil from the oil galley in the back of the block goes to the guage to tell you your pressure if it reads ok and isnt leaking then you are good to go as is ...have never seen a mechanical temp guage that had water running to the guage it is usually a ether filled bulb that operates that guage