Car temperature lights comes on?

I changed the thermostat and the water pump and all of the radiator hoses .

I hear a hissing sound behind the alternator, could it be the radiator or what is it I think monday Its going to a shop if I have to
Car temperature lights comes on?
Until it is properly pressure tested and cooling fans checked, my guess is as good as anybodies as to why it's getting hot. Year, make and model (engine size is good) would help. Some engines need to be bled properly before they cool properly.