Hard to tell from the pics, but is your fan completely inside the shroud, or is it halfway out? For it to work best, it needs to completely circle the fan, and the fan blades need to be sticking out of the shroud about halfway. You need all the airflow to come through radiator, none getting around the sides. Without the shroud circling the fan, you have turbulence at the bottom side causing the air to stagnate there. An easy test is take a sheet of paper and place it at various places on the front of the radiator, you should be able to see where the suction of the fan is greatest. The mechanical fan should be able to cool it fine. It will move more air than an electric fan if set up right.