cooling system has been replaced

Is it really hot? Can you tell? Is it boiling over? If not, you could have a faulty temperature sending unit. If it IS actually hot, boiling over, etc...then start thinking you haven't purged the air out of the cooling system, OR you have a cylinder head or head gasket issue. Or, you could have a cooling fan failure.

these motor are famous for a leak at the intake manifold - are you having to add to the coolant level?