I have my fathers 1951 TO 20, serial # 44763. While mowing on a hot day, I heard gas hissing out of the gas tank. When I removed the cap gas gushed out of the tank like a fountain. Have you heard of this before, is there a solution for it?
I can’t say this with enough emphasis, if that ever happens again, DO NOT REMOVE THE GAS CAP, turn the tractor the off. If possible get it to an area where it is not likely to set the field on fire.
Yes, the gas was boiling in the tank, a very dangerous situation and one that could have caused a fire and badly burned you. There have been some major law suits over this, and it caused International Harvester and Ford to issue a recall for all gas powered tractors manufactured to replace the gas cap with special gas caps that prevent this from happening.
In the case of the Ford 9N/2N/8N, etc, the fuel tanks had a vent separate from the gas cap, and used an unvented cap. The replacement cap which you could get for free for several years had a vent, and a special baffle to prevent gas from bubbling out. You should be able to purchase one of these from a New Holland dealer today but it should not be necessary if you have the proper manifold, a good working original vented gas cap, and an engine that is operating at normal temperatures.
I suspect your engine was running hot, and the radiator is probably in need of a good cleaning to remove chaff and debris from the fins. It may also need a good flushing,and a proper thermostat. You should also check the routing of the gas line to the carburetor, when the gas line runs close to or touches the manifold that further heats the gas. Last but not least, what manifold is on your tractor.
The TO/MF-35 manifold has been sold for years as a replacement for the TO-20 and TO-30. That manifold sits closer to the fuel tank, and covers a larger area of the tank surface than the original style manifold. That manifold has a heat shield over it when it is installed in the TO/MF-35. That heat shield deflects the heat. The 35 manifold sticks out farther than the original TO-20/30 manifold, and has a 3 bolt flange to attach the exhaust pipe. I can send you a picture if you need additional information. So, make sure the tractor cooling system is performing correctly.
Purchase a genuine Massey Ferguson vented gas cap or consider purchasing one of the New Holland caps for the 9N/2N/8N. Check the manifold and replace it with the correct original style which is now available from a number of sources including Steiner Tractor Parts. In the mean time, be very careful, and don’t try to remove the gas cap when the gas is boiling or bubbling out of the cap. Do not try to fill the tank when the engine is hot.