Well the tanks are made of injection molded black plastic and probably have a melting point of 400 degrees F or so. Some posters have said their tractors got "Red HOT" which to them means anything that is really hot. To a welder or metal worker "red hot" means a specific temperature where steel actually glows red which is 1400 deg. F, IIRC but a lot of people misuse the phase as they never went to metal shop in school. Hydraulic oil can certainly get boiling hot if constantly being pumped through relief valves at working pressure and the case it is in will get just as hot. They probably saved two bucks a tractor using plastic instead of steel and don't have to worry about rust in the tank ever.
Oil will boil at a much higher temp then water, what the limit is before it flashes over and explodes I don't know. The real question is what is causing the pumps and valves to work overtime superheating the oil in the first place. Is it a bad O-ring in the 3PH piston assembly or an SCV valve that doesn't fully close when the handle is in the closed position? If it's just a deaf operator hitting a valve with his maxi butt every time he looks back at the tool he's pulling they might need to move the SCV levers further out from the seat.
