2000 Jeep Cherokee

Temperature gauge on instrument panel was wavering between midpoint and red warning line for a few days. The car would not produce warm air (heat) while idling, but then would when I'm driving. After a few days of this, the gauge light came on on the instrument panel as the temp gauge hit the red zone. I replaced the thermostat, but that made no difference. The top radiator hose bulges at the end where it connects to the thermostat housing. After the car is shut down, the hose returns to its normal size. Is it possible that the problem is with the coolant sensor? Is there an easy test I can do to see if the radiator is clogged?