The Major Factor Governing Cooling System Heat Transfer
Cooling system heat transfer is governed by a single major factor-the heat load to the cooling system.  Under “steady-state” conditions, the heat load to the cooling system (the heat rejected by the engine to the cooling system) will be transferred to the cooling air by the radiator no matter how good or how poor the radiator.  So, if both a “poor” radiator and a “good” radiator will both transfer the same heat load to the cooling air, how can we say that one radiator has better heat transfer performance than the other? 
The answer is that, under “steady-state” conditions, with a “good” radiator in the cooling system, the radiator inlet temperature will stabilize at a lower temperature than a “poor radiator” in place.  The “poor radiator may be so poor that its coolant temperature may rise to the boiling point resulting in engine overheating.