At this point I would go ahead and have the radiator rodded, or replace it with one that you know is good. With the radiator out, you might also do the pump if there is budget for it.

I recommend this because you are overheating when there is plenty of air moving through the radiator, which says that the problem is insufficient movement of coolant either due to a failing water pump or a clogged radiator.

The fact that your radiator is cool at the bottom is a good clue that it is the problem.

Have also heard good things about adding Water Wetter from Redline to the coolant.

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe