Why is the main top hose from the radiator to the engine blowing up like a balloon?

More than likely, the thermostat is stuck. The thermostat is a valve that is supposed to allow water from the radiator to flow through the engine block. As the temperature rises, the thermostat opens and water from the radiator flows through the engine block and draws off heat.

If the thermostat is stuck closed, the water cannot flow, no matter how hot it gets. The pressure builds and the upper radiator hose can expand to a point. Eventually the hose will rupture.

Have an experienced mechanic replace the thermostat and the hose.