The older tractors will not have safety shut off devices. The newer computerized controlled tractors will have audible alarms and in many cases, these controls will automatically shut the engine down when excessive temperature readings are present.
A tractor's cooling system comprises of several components. There is a radiator, a radiator fan, water pump, lower radiator hose, upper radiator hose, a thermostat, and a liquid that flows through the engine, to the radiator where it is cooled, and then recalculated back into the engine to continue the cooling process.
The first step in diagnosing an overheating problem is to ensure that there is enough fluid in the radiator. This can be checked by looking in the overflow container. If that is filled, and there is no blockage from the radiator to the overflow container, then the engine must be allowed to cool. Once cooled, the radiator cap should be removed and the radiator checked for fluid.
If there is a fluid shortage, then the cause of the shortage needs to be identified. A damaged lower and upper radiator hose can be changed. The clamps on the system can be tightened or changed.
For fluid shortage, there should be visible leaks around the failed component, either the hoses, a leaking radiator, or broken water pump. Should there be no visible leaks and missing cooling fluid, then this can indicate a damaged cylinder head gasket that is allowing the fluid to either leak into the engine, or be pulled into the combustion chamber, burnt, and then exhausted.
The thermostat, a simple device, is located directly in the path of the flowing liquid. It contains a bi-metallic disc, that opens when immersed in fluid of a high temperature, and closes when the temperature of the fluid reduced below a predetermined level. Typically, most thermostats will fail in an open manner, thereby allowing overcooling rather that the opposite, overheating.
A simple way to test the thermostat is to put it into a container of water and bring that container to a boil on a stove, or hotplate. As the water temperature reaches boiling, the thermostat should begin to open. If it doesn't, then it needs to be changed.
Other sections of the cooling system not discussed here are the water pump, and the radiator, gauges and radiator cooling fan systems.