What would cause my camery to over heat after just replacing the radiator and fixing what was originally causing problems? There is one minor leak on the top of my coolant container,is there pressure in this plastic container for coolant when the car warms up? Could they have made a mistake with the radiator? I 'm at 185,000 miles. It drives fine and doesn't make noise except for occasionally on start where it sounds like a louder muffler. Please and thanks? Cat converter have any reason for this?

Also would like to add that it's the 4 cyl

Did you change the thermostat?
Does this have an electric fan, and does it appear to work?

It has an electric fan, and the water pump seems new so I think that the thermostat should be new, The fans don't appear to come on even after being heated up, Id also like to add the coolant compartment gets very hot and I smell burning (antifreeze I think) would this all happen because of the fan? Many thanks!