Pulled into parking lot with steam pouring out the overflow hose. Subsequent filling and testing and engine continues to overheat. Noticed that when engine is brought up to operating temperature top radiator hose is "cool" to the touch while bottom radiator hose is hot, hot, hot and then the "boilover" begins again. What do you think? Faulty thermostat?

Turn that around, the radiator hose coming from the TOP of the radiator is hot, hot, hot while the hose coming from the BOTTOM of the radiator is "cool to the touch" at engine operating temperature. Sorry for the turnaround, fatigued from lack of sleep.