If the top hose is hot and the bottom hose isn't, then your thermostat may not be opening to let the coolant circulate. I have also seen thermostats break at the top where they are held together, wich causes strange things to happen in the cooling system. Bottom line: a thermostat is cheap and easy to change, I would start there. Remove the thermostat and if it isn't physically broken,put it in a pot of hot water and use a theremometer to check the temp of the water. Wait for the thermostat to open and note the temp. If the stat opened at the temp stamped in the unit it is ok, if it hasn;t opened and the water is alot hotter than the temp rating of the stat,replace it.