[Canuk]

there are 5 items that overheating on a car. Yes there are lots of others from collapsed hoses to dragging brakes but not very often.

Thermostat
Water pump
Coolant level
Cooling fan
Radiator.
Since you had the problem prior to the engine change out you should rule out thermostat, water pump and coolant level as all should have replaced and checked with the new engine.

Radiator could be plugged internally or externally. Externally can be fixed with a water hose and lots of water sprayed all over the fins.

It is most likely the cooling fan not starting or running at speed or not getting proper signal from engine temperature sensors or the A/C pressure sensor. I would try to run the car with A/C on and A/C off to see if there is a difference.

 

[Canuk]

Eco does not turn off the a/c it just lowers fan speed and a/c performance. I tried economy on several long trips and found it was a pain.

On a long trip with temperature in high 30's cabin could not cool down enough, turned off the eco and bang the fan started blowing faster and cabin became comfortable.
Tried again on a long trip in cooler weather and eco could not maintain speeds in the mountains.
So after 2 long tries I am back to sport mode all the time except in winter if there is snow or ice.

 

[Canuk]

Try to see if the car overheats with A/C running or not.

Good luck and PLEASE get back to us on what the mechanic finds. So many pose a serious problem and drop out of sight.

 

[Canuk]

Thanks for getting back to us