Why does my car still overheat?

Why is my car still overheating? Since the last overheating fried the engine 2
weeks ago, I replaced all of this: engine (with low mileage used), radiator,
ignition coils, and fuel pump. $3,700 later, it is still overheating. Why? The
engine seller guaranteed the engine for 2 years EXCEPT overheating. What
does he know that I don't?

I am the second owner of my V6 Camry convertible. The previous owner
said that even though there were 150,000 miles on the car, it had a new
engine from Japan with only 40K miles on it. I never knew why the engine
was replaced. Now the car has 180,000 miles.

If anyone has any idea why the engine still overheats or who is responsible
for further repairs: the mechanic or me, I would appreciate your wisdom and
input.